upper ocean response to typhoon choi wan as measured by the kuroshio extension observatory mooring 1 the kuroshio extension observatory keo is a highly instrumented moored reference station located at 32 3 n 144 5 e in the recirculation gyre south of the kuroshio extension on 19 september 2009 the eye of typhoon choi wan international designation 0914 passed 40 km to the southeast of the keo surface mooring hourly meteorological and physical oceanographic measurements together with 3 hourly air sea carbon dioxide observations telemetered from keo in near real time show the evolution of the upper ocean and its associated air sea fluxes during the passage of this storm and its aftermath during the approach of the storm the mixed layer freshened because of intense rainfall this was followed by a large outgassing of co2 rapid cooling and an increase in salinity although these changes in mixed layer properties imply substantial entrainment they were accompanied by upwelling and ultimately a temporary 20 m shoaling of the mixed layer this upwelling which was observed at all depths including the deepest sensor near 500 m was coincident with the onset of near inertial oscillations in the mixed layer currents after the typhoon passed inertial pumping caused 15 20 m amplitude vertical displacements throughout the top 500 m that continued for at least 6 days a large oceanic response was observed in this case even though the eye of choi wan passed to the right of keo resulting in winds rotating cyclonically with time in opposition to the anticyclonic rotating near inertial currents

seasonal changes in planktonic foraminifera in the northwestern north pacific ocean sediment trap experiments from subarctic and subtropical gyres abstract upper ocean environments such as seawater temperature salinity thermal structure in the water column light intensity and food supply affect the assemblage of planktonic foraminifera since detailed information on planktonic foraminifera was not available for the northwestern north pacific we examined seasonal changes in fluxes and composition of planktonic foraminifera there data were collected by sediment traps deployed at three sites site 50n 50 01 n 165 02 e site knot 43 58 n 155 03 e and site 40n 39 60 n 165 00 e in this area in order to better understand the relationship between the foraminiferal assemblage and surface ocean environments although each planktonic foraminiferal species showed specific seasonal variations in flux some exhibited similar flux profiles in order to define these more accurately correlations among species were calculated and the foraminiferal species classified into four groups 1 group a subpolar species neogloboquadrina pachyderma globigerina quinqueloba globigerina bulloides and globigerinita glutinata 2 group b subtropical and tropical species globigerinoides ruber and globigerinoides sacculifer 3 group c post upwelling species neogloboquadrina dutertrei and 4 group d deep water species globorotalia scitula and globorotalia truncatulinoides the common environments for each period based on foraminiferal production and composition were observed among the three sites based upon predominant foraminiferal groups total foraminiferal fluxes tffs organic matter om fluxes and hydrographic conditions including sea surface temperatures sst and thermal structure the surface ocean environments in the northwestern north pacific could be generalized into five types type i is characterized by a dominance of group b with low tffs under high sst and type ii is marked by a high flux of group a on the other hand type iii shows low tffs and low om fluxes due to low insolation during winter type iv represents a high flux of group a and group d at site 40n under a well mixed surface ocean and type v is characterized by a prominent peak of group c under a developed thermocline a comparison of annual mean foraminifera fluxes at 50 n between the northwestern site 50n and the northeastern north pacific station papa during the normal cold mode demonstrated higher fluxes of foraminifera at site 50n due to higher nutrient concentrations the results also showed that g bulloides is not always a proxy for upwelling and that n pachyderma is not solely controlled by seawater temperature in the northwestern pacific where the surface water is enriched in nutrients the fluxes and composition of foraminifera suggest that similar ocean environments are expected in large areas of the northern north pacific from site knot to station papa during the warm mode which is affected by el nino events

porosity and size gradation of saturated gravel with percolated fines this is the accepted version of the following article nunez gonzalez f martin vide j p kleinhans m g 2016 porosity and size gradation of saturated gravel with percolated fines sedimentology 63 1209 1232 doi 10 1111 sed 12257 which has been published in final form at http onlinelibrary wiley com doi 10 1111 sed 12257 abstract

surface based transport model for mixed size sediment we present a transport model for mixed sand gravel sediments fractional transport rates are referenced to the size distribution of the bed surface rather than subsurface making the model completely explicit and capable of predicting transient conditions the model is developed using a new data set of 48 coupled observations of flow transport and bed surface grain size using five different sediments the model incorporates a hiding function that resolves discrepancies observed among earlier hiding functions the model uses the full size distribution of the bed surface including sand and incorporates a nonlinear effect of sand content on gravel transport rate not included in previous models the model shares some common elements with two previous surface based transport models but differs in using the full surface size distribution and in that it is directly developed from a relatively comprehensive data set with unambiguous measurement of surface grain size over a range of flow transport rate and sediments

modern distribution patterns of planktonic foraminifera in the south china sea and western pacific a new transfer technique to estimate regional sea surface temperatures abstract we present 30 new planktonic foraminiferal census data of surface sediment samples from the south china sea recovered between 630 and 2883 m water depth these new data together with the 131 earlier published data sets from the western pacific are used for calibrating the simmax 28 transfer function to estimate past sea surface temperatures this regional simmax method offers a slightly better understanding of the marginal sea conditions of the south china sea than the linear transfer function fp 12e which is based only on open ocean data however both methods are biased toward the tropical temperature regime because of the very limited data from temperate to subpolar regions the simmax formula was applied to sediment core 17940 from the northeastern south china sea with sedimentation rates of 20 80 cm ka results revealed nearly unchanged summer temperatures around 28 c for the last 30 ky while winter temperatures varied between 19 5 c in the last glacial maximum and 26 c during the holocene during termination 1a the winter estimates show a younger dryas cooling by 3 c subsequent to a temperature optimum of 24 c during the bolling allerod estimates of winter temperature differences between 0 and 100 m water depth document the seasonal variations in the thickness of the mixed layer and provide a new proxy for estimating past changes in the strength of the winter monsoon

predicting incipient motion including the effect of turbulent pressure fluctuations in the bed 1 incipient motion of particles on a river bed can in principle be understood and predicted from a balance of the forces acting on the particles on a natural river bed the exposure of particles to the flow is variable the effect of exposure on the initiation of motion including the case of deep embedding is studied in this paper so far the turbulence induced lifting force has been derived exclusively from examinations of the surface flow the understanding of destabilization processes of the riverbed is improved when turbulence induced vertical pressure gradients in the upper sediment layer are included this is particularly important for particles that lie in the lee of larger ones an analytical solution for the critical shields parameter of spherical particles is found including the effects of pressure fluctuations in the bed macroscale flow structures average bed slope and shallow flow existing laboratory data designed to test the effect of exposure and roughness conditions are in excellent agreement with the new model

numerical simulations of tropical cyclone ocean interaction with a high resolution coupled model the tropical cyclone ocean interaction was investigated using a high resolution tropical cyclone ocean coupled model the model design consisted of the noaa geophysical fluid dynamics laboratory tropical cyclone prediction model which was coupled with a multilayer primitive equation ocean model coupling between the hurricane and the ocean models was carried out by passing into the ocean model the wind stress heat and moisture fluxes computed in the hurricane model the new sea surface temperature sst calculated by the ocean model was then used in the tropical cyclone model a set of idealized numerical experiments were performed in which a tropical cyclone vortex was embedded in both easterly and westerly basic flows of 2 5 5 and 7 5 m s 1 with a fourth experiment run with no basic flow specified initially the profile of the tangential wind for hurricane gloria at 1200 utc 22 september 1985 was used as the initial condition of the tropical cyclone for each of the experiments the model ocean was initially horizontally homogenous and quiescent to clarify the impact of the ocean response to the hurricane s behavior analogous experiments were also carried out with the sst kept constant control cases the experiments indicated that the cooling of the sea surface induced by the tropical cyclone resulted in a significant impact on the ultimate storm intensity due to the reduction of total heat flux directed into the tropical cyclone above the regions of decreased sst the sea surface cooling produced by the tropical cyclones was found to be larger when the storms moved slower in the experiments run without an initial basic flow the maximum sst anomaly was about 5 6 c with a resulting difference in the minimum sea level pressure and maximum surface winds of 16 4 hpa and 7 m s 1 respectively in contrast in the experiments run with the 7 5 m s 1 basic flow the maximum sst anomalies ranged from about 2 6 to 3 0 c with a difference in the minimum sea level pressure and maximum surface winds of about 7 3 hpa and 2 7 m s 1 the tropical cyclone ocean coupling significantly influenced the storm track only for the case with no basic flow and the 2 5 m s 1 easterly flow in these cases the storm with the ocean interaction turned more to the north and east no basic flow or the north 2 5 m s 1 easterly flow of the experiments with constant sst in the first case the storm by 72 hours was located over 70 km to the east southeast of the control case a possible explanation for this track deviation is related to a systematic weakening of the mean tangential flow at all radii of the storm due to the interaction with the ocean and resulting alteration of the beta drift

the 3d oceanic mixed layer response to hurricane gilbert upper ocean heat and mass budgets are examined from three snapshots of data acquired during and after the passage of hurricane gilbert in the western gulf of mexico measurements prior to storm passage indicated a warm core eddy in the region with velocities of o 1 m s21 based upon conservation of heat and mass the threedimensional mixed layer processes are quantified from the data during and subsequent to hurricane passage horizontal advection due to geostrophic velocities is significant in the eddy regime suggesting that prestorm oceanic variability is important when background flows have the same magnitude as the mixed layer current response storm induced near inertial currents lead to large vertical advection magnitudes as they diverge from and converge toward the storm track surface fluxes estimated by reducing flight level winds to 10 m indicate a maximum wind stress of 4 2 n m22 and a heat flux of 1200 w m 22 in the directly forced region the upward heat flux after the passage of the storm has a maximum of 200 w m22 corresponding to a less than 7 m s21 wind speed entrainment mixing across the mixed layer base is estimated using three bulk entrainment closure schemes that differ in their physical basis of parameterization entrainment remains the dominant mechanism in controlling the heat and mass budgets irrespective of the scheme depending on the magnitudes of friction velocity surface fluxes and or shear across the mixed layer base the pattern and location of maximum entrainment rates differ in the directly forced region while the general area of maximum entrainment is in the right rear quadrant of the storm shear induced entrainment scheme predicts a narrow region of cooling compared to the the stressinduced mixing scheme and observed sst decreases after the storm passage the maximum contribution to the mixed layer dynamics is associated with shear induced entrainment mixing forced by near inertial motions up to the third day as indicated by bulk richardson numbers that remained below criticality thus entrainment based on a combination of surface fluxes friction velocity and shear across the entrainment zone may be more relevant for three dimensional ocean response studies

oxygen isotopic composition of multiple species of planktonic foraminifera recorders of the modern photic zone temperature gradient abundances of 12 species of planktonic foraminifera collected in two plankton tows from the east tropical atlantic are compared to the chlorophyll content and the temperature of the sea water from which they were collected as expected from previous work in the tropics all dominant tropical species occur in greatest abundance within the photic zone many species occur in greatest abundances in the seasonal thermocline in association with the maximum chlorophyll concentration while a few algal symbiont bearing species occur in greatest abundance in the mixed layer the 18o measurements of planktonic foraminifera shells from core top sediment samples confirm the vertical stratification within the photic zone that is suggested by the relationship between hydrography and abundances found in the plankton tows and found in the statistical study by ravelo et al 1990 comparison between the measured 18o values of planktonic foraminifera with the predicted 18o profiles of the overlying water column at three core locations indicate that species abundances in the sediment record the seasonally integrated conditions of the photic zone and suggests that the abundance of a species in the sediment depends on whether the preferred ecological conditions of that species may be found within the photic zone of the overlying water column sometime during the year species which calcify below the photic zone have only trace relative abundances finally it appears that the total range of 18o values of the dominant species approximates the predicted annual 18o of calcite range in the upper 80 m of the water column

spatially averaged open channel flow over rough bed in this paper it is suggested that the double averaged in temporal and in spatial domains momentum equations should be used as a natural basis for the hydraulics of rough bed open channel flows especially with small relative submergence the relationships for the vertical distribution of the total stress for the simplest case of 2d steady uniform spatially averaged flow over a rough bed with flat free surface are derived these relationships explicitly include the form induced stresses and form drag as components of the total stress using this approach we define three types of rough bed flows 1 flow with high relative submergence 2 flow with small relative submergence and 3 flow over a partially inundated rough bed the relationships for the double averaged velocity distribution and hydraulic resistance for all three flow types are derived and compared with measurements where possible the double averaged turbulent and form induced intensities and stresses for the case of regular spherical segment type roughness show the dominant role of the double averaged turbulence stresses and form drag in momentum transfer in the near bed region

the variability of critical shear stress friction angle and grain protrusion in water worked sediments the erodibility of a grain on a rough bed is controlled by among other factors its relative projection above the mean bed its exposure relative to upstream grains and its friction angle here we report direct measurements of friction angles grain projection and exposure and small scale topographic structure on a variety of water worked mixed grain sediment surfaces using a simple analytical model of the force balance on individual grains we calculate the distribution of critical shear stress for idealized spherical grains on the measured bed topography the friction angle projection and exposure of single grain sizes vary widely from point to point within a given bed surface the variability within a single surface often exceeds the difference between the mean values of disparate surfaces as a result the critical shear stress for a given grain size on a sediment surface is characterized by a probability distribution rather than a single value on a given bed the crtitical shear stress distributions of different grain sizes have similar lower bounds but above their lower tails they diverge rapidly with smaller grains having substantially higher median critical shear stresses large numbers of fines trapp ed within pockets on the bed or shielded by upstream grains are effectively lost to the flow our calculations suggest that critical shear stress as conventionally measured is defined by the most erodible grains entrained during transient shear stress excursions associated with the turbulent flow this implies a physical basis for the indeterminacy of initial motion these observations suggest that transport rate shear stress relationships may be controlled in part by the increasing numbers of grains that become available for entrainment as mean shear stress increases they also suggest that bed textures and grain size distributions may be controlled within the constraints of an imposed shear stress and sediment supply regime by the influence of each size fraction on the erodibility of other grain sizes present on the bed

fluxes of planktic foraminifera in response to monsoonal upwelling on the somalia basin margin abstract sediment trap samples collected off somalia bi weekly from early june 1992 through mid february 1993 show large seasonal variations in the shell flux and species composition of planktic foraminifera these variations mirror the monsoon driven circulation which resulted in massive upwelling and offshore eddy transport in summer during the sw monsoon june september and accounted for nearly 90 of the estimated annual shell flux of planktic foraminifera g bulloides dominated the sw monsoon along with g glutinata t quinqueloba n dutertrei and t iota in a fauna rich species but with a low diversity and equitability during the autumn intermonsoon november december the ocean became stratified and the nutrient exhausted whereas during the ne monsoon january march a warm surface mixed layer developed with the nutrients entrained by deep wind mixing it was dominated by g ruber in association with g tenella g aequilateralis g trilobus g sacculifer and g menardii in a fauna poorer in species but with a higher diversity and equitability consequently the ratio in the abundance of g bulloides and g ruber follows the monsoonal cycle closely as both species persist throughout the year only the rare g theyeri seems to be restricted to the sw monsoon in october at the end of the sw monsoon the trap at 265 m above the bottom intercepted massive amounts of fine grained carbonate m resuspended from the shelf and upper slope it contained extreme fluxes of bioclastic fragments benthic foraminifera and benthic ostracods as well as enhanced fluxes of small sized planktic foraminifera m notably g rubescens integrated over the year the species composition intercepted by the trap shows a very good match with the shell fauna in a core top sediment from the same site apparently the year estimated monsoonal record of planktic foraminifera which is strongly dominated by the sw monsoon production survives burial intact consequently the species composition of planktic foraminifera and measures such as the bulloides ruber ratio can be applied as a proxy for past changes in the intensity of the sw monsoon off somalia compared to the modern condition

living planktic foraminifera in the central tropical pacific ocean articulating the equatorial cold tongue during la nina 1992 abstract in cold tongue conditions of august september 1992 living planktic foraminifera in the equatorial pacific tracked circulation featuresand phytoplankton abundance an equatorial assemblage associated with the cool and productive equatorial region contained g bulloides a species often associated with tropical coastal upwelling as well as the nonspinose herbivores g menardii g glutinata p obliquiloculata and n dutertrei previously associated with equatorial environments within surface subtropical waters poleward of 5 n and 5 s g sacculifer g ruber and g conglobatus dominated foraminiferal populations these species have successfully adapted to oligotrophic conditions by exploiting dinoflagellate endosymbionts high standing stocks of these species in equatorial regions suggest that they can also thrive within equatorial light levels and temperatures a deep southern assemblage dominated by nonspinose g conglomerata and g tumida and spinose g aequilateralis had a subsurface maximum at 80 200 m outside of active upwelling and outcropped to the surface at 1 s from el nino to cold tongue conditions equatorial fauna reflected higher primary productivity and an increase in the role of advection by the south equatorial current

thermocline dynamics in the northwestern tropical pacific over the past 700 kyr abstract variations in thermoclinal conditions play an important role in the evolution of the western pacific warm pool wpwp and in connecting the tropical and extratropical regions of the pacific ocean however secular thermoclinal changes in the northwestern part of the wpwp and their forcing mechanisms are not yet well understood particularly on orbital timescales in this study we report thermoclinal variation at site md06 3047 b in the western philippine sea over the last 700 kyr our data show that variations in thermocline temperature and salinity in the study area were correlated with changes in earth s obliquity with warmer and saltier colder and fresher thermocline waters corresponding to high low earth axial obliquity at high obliquity increases in thermocline temperature and salinity may have been linked to advection of warm north pacific tropical water in the study area a lower higher vertical temperature gradient in the upper water column suggests a deeper shallower thermocline during glacials interglacials the main factor leading to thermoclinal deepening during glacials was strengthening of the east asian winter monsoon eawm and more la nina like conditions may have contributed to concurrent subsurface warming and thus thermoclinal deepening in phase thermoclinal deepening in the northern and peri equatorial southern wpwp during glacial stages may have been triggered by changes in glacial boundary conditions such as increased ice sheet thickness through intensification of the eawm and strengthening of the tropical trade winds

variability of mixed layer depth in kuroshio oyashio extension region 2005 2006 1 in december 2005 the winter monsoon was abnormally strong around japan therefore it was expected that the cooling effect on the upper layer of the ocean would be very strong however the mixed layer depth mld in the kuroshio oyashio extension region was not as deep as those observed during the last four winters we investigated the reason for the shallow mld by using a one dimensional turbulent closure model and the temperature and salinity data obtained using argo floats we found that summer heating plays an important role in the determination of the maximum mld in 2005 the heat storage rate was very high from july to october since summer heating was significantly stronger than those during the other summers consequently a large vertical density gradient existed at the bottom of the mixed layer and prevented the deepening of the mixed layer

western equatorial pacific planktic foraminiferal fluxes and assemblages during a la nina year 1999 abstract a correlation between foraminiferal community dynamics and environmental conditions may provide a basis for establishing paleoclimatic proxies we studied planktic foraminiferal shell fluxes and assemblages in samples collected in three time series sediment trap deployments in the western equatorial pacific under la nina conditions from january to november 1999 eleven species contributed about 90 of the total flux in all traps two sites mt1 mt3 in the western pacific warm pool region wpwp were characterized by common occurrences of the species globigerinoides ruber globigerinoides sacculifer globigerinoides tenellus and neogloboquadrina dutertrei site mt5 farther to the east in the equatorial upwelling region had common occurrences of globigerina bulloides globigerinita glutinata and pulleniatina obliquiloculata very high abundances of g bulloides and g glutinata at mt5 indicate that equatorial upwelling eu occurred during the 1999 la nina the two western sites have similar assemblage compositions but mt1 135 e has the highest fluxes up to 3800 tests m 2 day 1 whereas mt3 145 e has fluxes below 2200 tests m 2 day 1 relatively high fluxes up to 3000 tests m 2 day 1 occur at site mt5 176 e where upwelling occurred the differences in faunal composition in the wpwp and eu might be attributable to differences in the way in which nutrients are supplied to the phytoplankton large amounts of suspended material are supplied to the wpwp by advection of waters passing through the coastal region of an archipelago whereas upwelling of nutrient rich waters enhances primary production in the eu at the westernmost site in the wpwp a peak in the g bulloides flux coincided with southward flow of the new guinea coastal current ngcc in late february but the highest g ruber flux coincided with northward flow of this current in late may thus the differences in species dominance at this location may be caused by monsoon driven variability in the flow direction of the nggc

upper ocean temperature response to hurricane felix as measured by the bermuda testbed mooring hurricane felix passed over the bermuda testbed mooring on 15 august 1995 providing a unique opportunity to observe the response of the upper ocean to a hurricane in the vicinity of bermuda felix was a particularly large hurricane with hurricane force winds over a diameter of about 300 400 km and tropical storm force winds over a diameter of about 650 800 km felix moved northwestward at about 25 km h21 with the eye passing about 65 km southwest of the mooring on 15 august peak winds reached about 135 km h21 at the mooring complementary satellite sea surface temperature maps show that a swath of cooler water by about 3 58 4 08c was left in the wake of felix with the mooring in the center of the wake prior to the passage of felix the mooring site was undergoing strong heating and stratification however this trend was dramatically interrupted by the passage of the hurricane as felix passed the mooring large inertial currents speeds of 100 cm s 21 at 25 m were generated within the upper layer the e folding decay timescale of the inertial currents was about 9 days the mixed layer depth was about 15 m before the arrival of felix and deepened to about 45 m within three days after felix s passage the temperature at 25 m decreased by approximately 3 5 8 4 08c large amplitude temperature oscillations 1 58c near the inertial period inertial pumping effect were set up by the hurricane in the seasonal thermocline resulting in vertical displacements of isotherms of approximately 15 m at 60 70 m comparative scale analyses of the upper ocean responses to hurricane felix and hurricane gloria 1985 indicate that they have several similarities

cold wake of hurricane frances 1 an array of instruments air deployed ahead of hurricane frances measured the three dimensional time dependent response of the ocean to this strong 60 ms 1 storm sea surface temperature cooled by up to 2 2 c with the greatest cooling occurring in a 50 km wide band centered 60 85 km to the right of the track the cooling was almost entirely due to vertical mixing not air sea heat fluxes currents of up to 1 6 ms 1 and thermocline displacements of up to 50 m dispersed as near inertial internal waves the heat in excess of 26 c decreased behind the storm due primarily to horizontal advection of heat away from the storm track with a small contribution from mixing across the 26 c isotherm sst cooling under the storm core 0 4 c produced a 16 decrease in air sea heat flux implying an approximately 5 ms 1 reduction in peak winds

cool la nina during the warmth of the pliocene the role of el nino southern oscillation enso in greenhouse warming and climate change remains controversial during the warmth of the early mid pliocene we find evidence for enhanced thermocline tilt and cold upwelling in the equatorial pacific consistent with the prevalence of a la nina like state rather than the proposed persistent warm el nino like conditions our pliocene paleothermometer supports the idea of a dynamic ocean thermostat in which heating of the tropical pacific leads to a cooling of the east equatorial pacific and a la nina like state analogous to observations of a transient increasing east west sea surface temperature gradient in the 20th century tropical pacific

shoaling of the western equatorial pacific thermocline during the last glacial maximum inferred from multispecies temperature reconstruction of planktonic foraminifera abstract glacial interglacial scale climate variability in the tropical pacific is often discussed with reference to modern el nino southern oscillation enso however proxy records show diverse results and result in inconsistent interpretations to investigate changes in the thermocline depth of the western pacific warm pool wpwp which is strongly related to the strength of the walker circulation this study conducted 18 o and mg ca analyses of multispecies planktonic foraminifera for the last 25 000 years habitat depths and calcification temperatures of seven foraminiferal species were estimated by comparing measured 18 o values with the predicted values by assuming isotopic equilibrium reconstructed mg ca based temperatures calculated with a newly calibrated multispecies equation showed 1 2 c larger cooling at the thermocline depth than that at the surface during the last glacial maximum lgm suggesting shoaling of the thermocline furthermore fresher surface water in the wpwp which is attributed to the suppressed evaporation by low sea surface temperature suggests the weakened deep atmospheric convection these results suggest that the walker circulation during the lgm was weaker than that during the late holocene

climatic evolution of the central equatorial pacific since the last glacial maximum this paper investigates paleoceanographic changes at a central equatorial pacific site 6 40 n 177 28 w since the last glacial maximum using planktic foraminifera assemblages together with the oxygen isotope 18o and mg ca compositions of three species globigerinoides sacculifer pulleniatina obliquiloculata and globorotalia tumida that dwell in the mixed layer upper thermocline and lower thermocline respectively while the mg ca derived temperatures of the mixed layer and lower thermocline varied within a narrow range from 18 ka onward the upper thermocline temperature increased by as much as 3 c during the last deglaciation 18 12 ka with a simultaneous decrease of 18o these changes are best explained by an enhanced mixing of the upper ocean and a reduced habitat depth separation between p obliquiloculata and g sacculifer during the 18 12 ka interval the planktic foraminifera assemblage during the same period resembles modern composition at subtropical central pacific sites that are strongly influenced by the northeasterly trades and north equatorial current nec we suggest that the study site presently under the control of the intertropical convergence zone itcz north equatorial countercurrent had been influenced by the northeasterly trades and nec during the 18 12 ka interval this interpretation is consistent with previous documentation of a more southerly location of the itcz during two northern hemisphere cooling events the heinrich stadial 1 and the younger dryas and implies that the mean annual position of the itcz was located south of the study site by at least 2 of latitude

forced stage response to a moving hurricane abstract the upper ocean s response to three hurricanes norbert 1984 josephine 1984 and gloria 1985 is examined using field observations and a numerical ocean model our goal is to describe the physical processes that determine the structure and amplitude of hurricane driven upper ocean currents all three of these northern hemisphere hurricanes produced a rightward biased response of the mixed layer current and transport this asymmetry arises because the wind stress vector rotates clockwise on the right side of the track and remains nearly parallel with the inertially rotating mixed layer current during most of the hurricane passage the maximum observed mixed layer current varied from 0 8 m s 1 in response to josephine which was a large but comparatively weak hurricane to 1 7 m s 1 in response to gloria which was very large and also intense these cases have been simulated with a three dimensional numerical model that includes a treatment of wind driven vertical mixing within the primitive

seasonal changes in species composition numbers mass size and isotopic composition of planktonic foraminifera settling into the deep sargasso sea abstract planktonic foraminifera recovered from six successive sediment trap samples collected over fourteen months at a depth of 3200 m near bermuda show varied responses to seasonal changes in the near surface hydrography these include changes in species composition and within species changes in number of individuals collected per unit time average size and weight of individuals and in oxygen and carbon isotopic composition a total of seventeen species were identified and eleven were sufficiently abundant for isotopic analysis in at least some of the samples the accumulations on the sea floor of some of these species can be expected to contain a strong seasonal component in their oxygen isotopic composition which may be utilized in paleoclimatic and paleo oceanographic reconstructions best suited to this purpose are those species which form their tests in isotopic equilibrium with surface water and whose abundance is confined to a portion of the year only the best examples are pulleniatina o bliguiloculata globigerinoides conglobatus and neogloboquadrina dutertrei globigerinoides ruber is a good estimator of the average surface water temperature because it occurs in rather even abundance throughout the year hastigerina pelagica though very abundant in surface water is practically eliminated even before arrival on the sea floor by partial resorption and structural weakening of the tests during gametogenesis orbulina universa globorotalia truncaltulinoides and globorotalia hirsuta show morphological and istopic evidence for contibnued calcification in deeper water after initial test formation near ther surface globigerina bulloides represents the most striking example of oxygen isotopic disequilibrium with sea water

active interactions between turbulence and bed load conceptual picture and experimental evidence 1 this paper reports results from experiments with simultaneous measurement of areal bed load sediment concentration and water velocity horizontal and vertical components made at 1 5 particle diameters above the mean bed the same spatial and temporal scales were employed to measure the kinematic properties of flowing water and sediments the obtained data covering a range of low sediment discharges were analyzed in terms of bulk statistics autocorrelation and cross correlation functions and quadrant decomposition of fluctuations at the lowest transport rates the motion of sediment particles was found to be mostly associated with sweep events however with increasing flow rate and bed load discharge the process mechanics changed and the transport of sediments was also found to be significantly correlated with ejections the obtained results are integrated into a conceptual picture attempting to bridge previous depictions of the bed load transport mechanics

comparison of seasonal flux variations of planktonic foraminifera in sediment traps on both sides of the ryukyu islands japan variations in the fluxes of planktonic foraminifera were analyzed based on sediment trap data collected over a period of 10 months from october 1994 to august 1995 at stations jast01 and jast02 located on both sides of the ryukyu islands japan station jast01 latitude 27 23 n longitude 126 44 e was deployed at a depth of 1000 m in the okinawa trough east china sea along the flow axis of the kuroshio current west of the islands whereas station jast02 latitude 25 4 n longitude 127 34 e was deployed at a depth of 3000 m in the ryukyu trench along the western margin of the northwest pacific east of the islands the total planktonic foraminiferal fluxes tffs in the eastern station were high in winter when the surface water column was vertically well mixed in contrast the tff peaks did not show significant seasonality in the western station but values fluctuated with the northwest southeast oscillation of the kuroshio axis among the 36 planktonic foraminiferal species identified in the trap samples globigerina bulloides globigerinita glutinata neogloboquadrina dutertrei pulleniatina obliquiloculata globigerinoides ruber globigerinoides sacculifer and globigerina falconensis exhibited a greater shell flux on both sides of the ryukyu island arc the fluxes of g ruber and g sacculifer increased synchronously with the seasonal warming of surface waters whereas that of g falconensis increased during winter when the water column was vertically well mixed as a result of the nw monsoon in contrast to these species which exhibited similar seasonal flux variation patterns at both stations the species g bulloides g glutinata n dutertrei and p obliquiloculata displayed different flux variations on both sides of the islands these fluxes seem to be regulated by phytoplankton productivity which is controlled by the vertical structure of the water column on the eastern ryukyu trench side and by the oscillation of the kuroshio axis on the western okinawa trough side lateral transport of suspended planktonic foraminiferal shells to the okinawa trough might exist but is not prominent enough to wipe out the original features of the planktonic foraminiferal flux the species g falconensis is an indicator of winter mixing on both sides of the ryukyu islands and may possibly be used as a proxy to trace the intensity of the paleo winter monsoon

controls on downstream variation in surficial sediment size of an outwash braidplain developed under high arctic conditions kaffioyra svalbard abstract the changes in morphology and surficial sediments of an outwash braidplain developed under high arctic conditions are closely related to geomorphic processes tectonic conditions and climate variations and are affected by the existence of permafrost these factors control the changes in river channel slope their morphology and active braidplain width which influence the downstream variation in grain size of outwash surficial sediments interdependence between these parameters has not previously been considered in relation to the spatial distribution of surficial sediments of outwash braidplain developed in the forefield of a retreating subpolar glacier in this study controls affecting the surficial lithology of the waldemar river outwash nw spitsbergen svalbard were recognised and indicated multiple correlations between the downstream changes in sediment texture the geomorphometry of distributary channels and outwash surface slope due to this the techniques of multivariate regression modelling artificial neural network and multivariate adaptive regression splines were used results show that observed relations between the sedimentary and morphological features indicate the existence of thresholds for downstream variation in bed material size which are not constant moreover the processes of sediment transport in an outwash braidplain are strictly related to shields stress which is proportional to changes in braidplain slope median grain diameter and sediment sorting in the proximal and middle zones of the outwash but is inversely proportional to median grain diameter in the distal zone contrary to shields bed material threshold entrainment model the results of this study will help understand outwash fan and plain evolution in paraglacial landscapes under conditions of changeable rate and source of sediment supply and transport capacity

incipient sediment motion at high slopes in uniform flow condition 1 this paper reviews the problem of the incipient motion of cohesionless particles in a high sloping water stream a theoretical analysis of the equilibrium of a gravel particle is developed by a deterministic approach with the introduction of the relative degree of exposure of the particle itself to the stream flow the parameter relative degree of exposure relates the positioning of a particle with the upstream one the problem of velocity distribution and the definition of drag coefficient is also revised to better account for low submergence the results of the theory are compared with a series of ad hoc experiments performed by c gregoretti

ocean response to a hurricane part i observations abstract the response of the ocean to hurricanes was investigated using aircraft deployable expendable current profilers axcp the goals were to observe and separate the surface wave and surface mixed layer sml velocities under the storms and to map the across track and along track velocity and temperature response in the mixed layer and thermocline custom instrumentation was prepared including slower failing axcps and the axcp equipment was installed on noaa wp 3d aircraft research flights were made into two 1984 hurricanes norbert in the eastern pacific off baja california 19 n 109 w and josephine off the east coast of the united states 29 n 72 w thirty one probes were deployed in each hurricane and about half the axcps provided temperature and velocity profiles most velocity profiles exhibited strong surface wave contributions slablike velocities in the sml strong shears beneath the sml and only weak flows in the upper thermocline separation of the surface gravity wave velociti

biological and chemical characteristics of high chlorophyll low temperature water observed near the sulu archipelago abstract according to ocean color remote sensing data a low phytoplankton biomass exists in the central parts of the sulu and celebes seas whereas higher concentrations of chlorophyll a are observed in the waters near the sulu archipelago which separates these water bodies these high chlorophyll a waters have lower temperatures than those of surrounding waters indicating vertical mixing of nutrient rich subsurface water that is attributable to the topographical features of the sulu ridge differences in photosynthetic parameters primary productivity and the phytoplankton community structure between the high chlorophyll area near the sulu archipelago and the oligotrophic basin area in the philippine sulu and celebes seas were investigated in november 2002 during the r v hakuho maru kh 02 4 cruise entrainment of subsurface water and vertical mixing by intense tidal flow from the sulu archipelago to the celebes sea created a low temperature high nutrient condition at the southeastern edge of the sulu ridge chlorophyll a concentrations greater than 2 g l 1 were observed at stations 5 15 km offshore at the edge of the sulu ridge this high chlorophyll tongue in the celebes sea showed high primary productivity it was 1 6 18 times higher than those measured in oligotrophic central basin regions of the philippine sulu and celebes seas microscopic observation of these high chlorophyll waters showed the dominance of chain forming large centric diatoms extension of high chlorophyll waters was not observed at the sulu sea side where the surface water salinity was lower than in the celebes sea and consequently prevented intrusion of the celebes sea water into the surface layer occasional extensions of productive chlorophyll rich surface water from the archipelagic zone to the surrounding basin area seems to be an important factor causing spatiotemporal variability in the phytoplankton biomass in the southern sulu sea and the western celebes sea

feedback between bed load transport and flow resistance in gravel and cobble bed rivers 1 to calculate bed load engineers often use flow resistance equations that provide estimates of bed shear stress in these equations on the basis of the estimate of the appropriate hydraulic radius associated with the bed only the bed roughness ks is commonly set as a constant whatever the bed load intensity however several studies have confirmed the existence of feedback mechanisms between flow resistance and bed load suggesting that a flow dependent bed roughness should be used therefore using a data set composed of 2282 flume and field experimental values this study investigated the importance of these feedback effects new flow resistance equations were proposed for three flow domains domain 1 corresponds to no bed load and a constant bed roughness ks d where d is a representative grain diameter whereas domain 3 corresponds to a high bed load transport rate over a flat bed with a constant bed roughness ks 2 6d between these two domains a transitional domain 2 was identified for which the bed roughness evolved from d to 2 6d with increasing flow conditions in this domain the darcy weisbach resistance coefficient f can be approximated using a constant for a given slope the results using this new flow resistance equation proved to be more accurate than those using equations obtained from simple fittings of logarithmic laws to mean values the data set indicates that distinguishing domains 2 and 3 is still relevant for bed load in particular the data indicate a slope dependence in domain 2 but not in domain 3 a bed load model based on the tractive force concept is proposed finally flow resistance and bed load equations were used together to calculate both shear stress and bed load from the flow discharge the slope and the grain diameter for each run of the data set efficiency tests indicate that new equations implicitly taking a feedback mechanism into account can reduce the error by a factor of 2 when compared to other equations currently in use showing that feedback between flow resistance and bed load can improve field bed load modeling

mean and near inertial ocean current response to hurricane gilbert abstract the three dimensional hurricane induced ocean response is determined from velocity and temperature profiles acquired in the western gulf of mexico between 14 and 19 september 1988 during the passage of hurricane gilbert the asymmetric wind structure of gilbert indicated a wind stress of 4 2 n m 2 at a radius of maximum winds rmax of 60 km using observed temperature profiles and climatological temperature salinity relationships the background and storm induced geostrophic currents re 750 m were 0 1 m s 1 and 0 2 m s 1 respectively a loop current warm core ring lcwcr was also located to the right of the storm track at 4 5 rmax where anticyclonically rotating near surface and 100 m currents decreased from 0 9 m s 1 to 0 6 m s 1 at depth the relative vorticity in the lcwcr was shifted below the local coriolis parameter by about 6 in a storm based coordinate system alongtrack residual velocity profiles from 0 to 4 rmax were fit to a dynamical model by least squares to isolate the near

permanent el nino like conditions during the pliocene warm period during the warm early pliocene 4 5 to 3 0 million years ago the most recent interval with a climate warmer than today the eastern pacific thermocline was deep and the average west to east sea surface temperature difference across the equatorial pacific was only 1 5 0 9 c much like it is during a modern el nino event thus the modern strong sea surface temperature gradient across the equatorial pacific is not a stable and permanent feature sustained el nino like conditions including relatively weak zonal atmospheric walker circulation could be a consequence of and play an important role in determining global warmth

theoretical development on the effects of changing flow hydraulics on incipient bed load motion 1 several decades of flume and field measurements have indicated that in rough turbulent flows the critical shields stress increases with increasing slope and associated decreasing relative depth this result contradicts the usual consideration of a decreased critical shields value on very steep slopes because of increased gravitational effects however recent studies have demonstrated that these experimental results could be reproduced with a force balance model if the classical logarithmic velocity profile was replaced with a velocity profile that was more compatible with available velocity measurements over gravel beds these measurements indicate the existence of a roughness layer that is a zone of almost constant velocity close to the bed whose properties mean velocity and turbulence depended on the flow s relative depth unfortunately velocity profile measurements for low relative depth associated with steep slopes are scarce and it is still difficult to include such flow properties in a force balance model flow resistance data on the basis of depth average velocity measurements are very common and cover a wide range of slopes and relative depths in this paper these data are used to fit a velocity profile including a roughness layer when used in a force balance model for incipient motion it adequately reproduced a data set composed of 270 critical shields values measured in a flume with near uniform sediments the relevance of this research to field problems is discussed using a data set composed of 92 critical shields stresses obtained from field measurements finally a model is proposed for field applications taking into account the slope effect

magnetic resonance imaging of coarse sediment abstract non destructive observation methods for coarse sediments are usually limited to two dimensions for instance in opened cores or at the surface we report a trial of a promising new method for three dimensional imaging of gravelly sediments magnetic resonance imaging mri mri maps contrasts in density and relaxation properties of protons which are very different for sediment and water in the pores images of glass bead mixtures show that the local porosity varies with sorting patterns or imperfect sample mixing illustrating the potential for this non destructive imaging method as a quantitative test we verify that a macroscopic sediment property porosity compares well to a standard lab determination and a recent model for predicting porosity for arbitrary grain size distributions finally we discuss potential applications and limitations of mri to porosity and permeability sedimentary structures benthic life and slow groundwater or mass flows

establishment of the western pacific warm pool during the pliocene evidence from planktic foraminifera oxygen isotopes and mg ca ratios abstract this study presents new evidence of when and how the western pacific warm pool wpwp was established in its present form we analyzed planktic foraminifera oxygen isotopes and mg ca ratios in upper miocene through pleistocene sediments collected at deep sea drilling program dsdp site 292 these data were then compared with those reported from ocean drilling program odp site 806 both drilling sites are located in the western pacific ocean dsdp site 292 is located in the northern margin of the modern wpwp and odp site 806 near the center of the wpwp three stages of development in surface water conditions are identified in the region using planktic foraminferal data during the initial stage from 8 5 to 4 4 ma site 806 was overlain by warm surface water but site 292 was not as indicated by the differences in faunal compositions and sea surface temperature sst between the two sites in addition the vertical thermal gradient at site 292 was weak during this period as indicated by the small differences in the 18 o values between globigerinoides sacculifer and pulleniatina spp during stage two from 4 4 to 3 6 ma the sst at site 292 rapidly increased to 27 c but the vertical thermal gradient had not yet be strengthened as shown by mg ca ratios and the presence of both mixed layer dwellers and thermocline dwellers finally a warm mixed layer with a high sst ca 28 c and a strong vertical thermal gradient were established at site 292 by 3 6 ma this event is marked by the dominance of mixed layer dwellers a high and stable sst and a larger differences in the 18 o values between g sacculifer and pulleniatina spp thus evidence of surface water evolution in the western pacific suggests that site 292 came under the influence of the wpwp at 3 6 ma the northward expansion of the wpwp from 4 4 to 3 6 ma and the establishment of the modern wpwp by 3 6 ma appear to be closely related to the closure of the indonesian and central american seaways

effects of riparian vegetation on topographic change during a large flood event rio puerco new mexico usa 1 the spatial distribution of riparian vegetation can strongly influence the geomorphic evolution of dryland rivers during large floods we present the results of an airborne lidar differencing study that quantifies the topographic change that occurred along a 12 km reach of the lower rio puerco new mexico during an extreme event in 2006 extensive erosion of the channel banks took place immediately upstream of the study area where tamarisk and sandbar willow had been removed within the densely vegetated study reach we measure a net volumetric change of 578 050 490 000 m3 with 88 3 of the total aggradation occurring along the floodplain and channel and 76 7 of the erosion focusing on the vertical valley walls the sediment derived from the devegetated reach deposited within the first 3 6 km of the study area with depth decaying exponentially with distance downstream elsewhere floodplain sediments were primarily sourced from the erosion of valley walls superimposed on this pattern are the effects of vegetation and valley morphology on sediment transport sediment thickness is seen to be uniform among sandbar willows and highly variable within tamarisk groves these reach scale patterns of sedimentation observed in the lidar differencing likely reflect complex interactions of vegetation flow and sediment at the scale of patches to individual plants

macroturbulent structure of open channel flow over gravel beds the turbulent structure of open channel flow over a mobile gravel bed was investigated in an 8 m long 0 3 m wide and 0 3 m deep tilting flume a flow visualization technique was used and complemented by measurements of flow velocity fluctuations near the bed the experiments reveal that turbulent flow consists of a sequence of large scale eddies with a vertical size close to the flow depth an average length equal to four to five depths and a width of about two depths the downstream motion of these eddies causes quasiperiodic fluctuations of the local flow velocity components the development of longitudinal troughs and ridges on the mobile bed and preferential transport of bed particles along troughs are related to the effect of the eddies the experimental results indicate that the depth scale eddies are an important turbulence mechanism contributing to sediment transport

vertical distribution and isotopic fractionation of living planktonic foraminifera from the panama basin a model1 2 which explains the vertical and seasonal distribution of planktonic foraminifera was developed using data from the western north atlantic and is comprised of three tenets 1 the conditions in the photic zone upper 80 100 m exclusively dictate planktonic foraminifera species composition and abundance throughout the water column 2 species are vertically stratified within the photic zone according to their temperature preference depth distribution according to temperature preference has been proposed by several authors3 based on isotope analyses of sediments due to seasonal temperature variations seasonal variations in the 18o composition of seawater and species specific isotope fractionation rigorous proof of this hypothesis cannot be provided from sediment analyses alone 3 the chlorophyll maximum is a major food source zone which is preferentially exploited by foraminifera our data from the panama basin which are presented here are confirmation of this model the panama basin in the eastern equatorial pacific which has a shallow and steep thermocline was sampled for living planktonic foraminifera a multiple opening closing net and environmental sensing system mocness 4 was used to collect 13 sets of eight vertically stratified oblique samples we report here the quantitative distribution and stable isotopic composition of planktonic foraminifera from four mocness tows taken over 5 days during august 1979 rv knorr cruise 73 at 5 20 n 8 50 w each tow consisted of eight samples which integrated 12 5 m intervals from 0 to 100 m for moc 126 25 m intervals from 0 to 200 m for moc 127 100 150 m intervals from 0 to 1 000 m on moc 128 and 250 m intervals from 0 to 2 000 m on moc 131

x ray computed tomography reveals that grain protrusion controls critical shear stress for entrainment of fluvial gravels the critical shear stress c for grain entrainment is a poorly constrained control on bedload transport rates in rivers direct calculations of c have been hindered by the inability to measure the geometry of in situ grains i e the shape and location of each grain relative to surrounding grains and the bed surface we present the first complete suite of three dimensional 3 d grain geometry parameters for 1055 water worked grains and use these to parameterize a new 3 d grain entrainment model and hence estimate c the 3 d data were collected using x ray computed tomography scanning of sediment samples extracted from a prototype scale flume experiment we find that 1 parameters including pivot angle and proportional grain exposure do not vary systematically with relative grain size 2 c is primarily controlled by grain protrusion not pivot angle and 3 larger grains experience larger forces as a result of projecting higher into the flow profile producing equal mobility we suggest that grain protrusion is a suitable proxy for assessing gravel bed stability

on the response of the ocean to a moving storm parameters and scales abstract this paper has two purposes one is to present a new and efficient multilevel numerical model for calculating the response of the ocean to a moving storm the second is to show how on a time scale of a few inertial periods following the arrival of the storm the maximum horizontal and vertical velocities found in the wake can be calculated using a linear ekman model and a knowledge of that part of the change in the depth of the wind mixed layer due to entrainment this is demonstrated over a range of experiments with the multilevel numerical model these integrate the full nonlinear equations of motion with realistic ocean stratification and involve substantial entrainment of water into the wind mixed layer it is also shown that on this time scale the horizontal currents are confined near the surface but that the vertical velocity field extends throughout the depth of the ocean it is shown in appendix b that the wind forcing need only be large or fast for the forced response not to feel t

validation of a stochastic digital packing algorithm for porosity prediction in fluvial gravel deposits porosity as one of the key properties of sediment mixtures is poorly understood most of the existing porosity predictors based upon grain size characteristics have been unable to produce satisfying results for fluvial sediment porosity due to the lack of consideration of other porosity controlling factors like grain shape and depositional condition considering this a stochastic digital packing algorithm was applied in this work which provides an innovative way to pack particles of arbitrary shapes and sizes based on digitization of both particles and packing space the purpose was to test the applicability of this packing algorithm in predicting fluvial sediment porosity by comparing its predictions with outcomes obtained from laboratory measurements laboratory samples examined were two natural fluvial sediments from the rhine river and kall river germany and commercial glass beads spheres all samples were artificially combined into seven grain size distributions four unimodal distributions and three bimodal distributions our study demonstrates that apart from grain size grain shape also has a clear impact on porosity the stochastic digital packing algorithm successfully reproduced the measured variations in porosity for the three different particle sources however the packing algorithm systematically overpredicted the porosity measured in random dense packing conditions mainly because the random motion of particles during settling introduced unwanted kinematic sorting and shape effects the results suggest that the packing algorithm produces loose packing structures and is useful for trend analysis of packing porosity

the hydrodynamics of particle clusters and sediment entrapment in coarse alluvial channels particles projecting from the bed of an alluvial channel distort the fluid stream to produce a distinctive pressure field this has considerable significance for both the entrapment and entrainment of other particles and is a primary cause of the widespread occurrence of pebble clusters and boulder shadows lift and drag forces are determined on clustered hemispherical particles of varying size in the wake of an obstructing particle both forces are shown to vary directly with particle separation in a linear fashion on the stoss side of the cluster drag is uniform regardless of the separation of the component particles but lift is shown to increase when particle separation is small so affecting stability this mutual interference of neighbouring clustered bed particles is a vital consideration of incipient motion and is shown by field evidence to cause a wide range in transport stage for particles of similar size and shape on average 46 of clustered particles are entrained by flood flow compared to 87 of particles in open plane beds the influence of clusters is a major determinant of sedimentary sorting

flume study of the effect of relative depth on the incipient motion of coarse uniform sediments an experimental study of the incipient motion of coarse uniform sediments was undertaken in an 8 m long by 0 3 m wide tilting flume the concept of critical shear stress for the initial motion of streambeds has been linked to the probability of sediment entrainment through the intensity of sediment transport the experiments have revealed that critical flow conditions for uniform sediment motion are dependent not only on the grain size but also on the ratio of flow depth to grain diameter a revised shields diagram relating critical stress grain reynolds number and depth to grain size ratio has been derived this has implications for the calculation of sediment transport rates design of stable alluvial channels and physical hydraulic modeling

spreading of near inertial energy in a 1 12 model of the north atlantic ocean near inertial energy in the ocean is thought to be redistributed by s dispersion whereby near inertial waves generated at the surface by wind forcing propagate downward and equatorward in this letter we examine the spreading of near inertial energy in a realistic 1 12 model of the north atlantic driven by synoptically varying wind forcing we find that 1 near inertial energy is strongly influenced by the mesoscale eddy field and appears to be locally drained to the deep ocean largely by the chimney effect associated with anticyclonic eddies and 2 the interior of the subtropical gyre shows very low levels of near inertial energy contrary to expectations based on the s dispersion effect

seasonal change in foraminiferal production in the western equatorial pacific warm pool evidence from sediment trap experiments seasonal changes in the flux of individual planktonic foraminifera in the deep ocean have been studied in the western equatorial pacific warm pool using material collected by sediment traps over a period of 1 yr 1991 1992 mean total foraminiferal fluxes tffs were 171 and 97 shells m 2 day 1 at sites n1 2 59 8 n 135 01 5 e and n2 4 07 5 n 136 16 6 e respectively the seasonal change in tffs was much higher than for organic matter om and carbonate fluxes the major species of planktonic foraminifera were pulleniatina obliquiloculata neogloboquadrina dutertrei globigerinoides sacculifer globigerinella aequilateralis and globigerinoides ruber symbiont bearing species and n dutertrei were predominant in the western equatorial pacific warm pool comparison between the warm pool and upwelling deep sea research ii 43 1996 1257 mar micropaleontology 33 1998 157 indicates that the foraminiferal assemblage trapped at the western equatorial pacific warm pool was comparable with the south equatorial and subtropical assemblages during a plankton tow study conducted at 140 w in 1992 it suggests that fairly oligotrophic conditions prevailed in the western equatorial pacific warm pool in association with terrestrial nutrient inputs or temporary mixing by wind bursts the om flux was more positively correlated with the 63 m carbonate fraction mainly composed of coccoliths r 0 87 and biogenic opal which suggests that om fluxes were more affected by phytoplankton productivity although food availability is generally important for foraminiferal production tffs were poorly correlated with om fluxes at sites n1 and n2 which is partly attributed to the significant influence of symbiont photosynthesis the 18o values of p obliquiloculata and n dutertrei showed maxima in association with high om fluxes during period 2 from august to october and period 4 from late december to april at site n1 reflecting thickening of the mixed layer following wind bursts g sacculifer showed a lunar reproduction cycle when between july and october carbonate production was more predominant than biogenic opal production a similar profile was evident for g ruber orbulina universa and g aequilateralis these four species are generally predominant at low latitudes therefore the lunar reproduction cycle may significantly affect the fluctuation in carbonate production in the equatorial ocean

critical shear stress of natural sediments the critical shear stress of individual fractions ci in unimodal and weakly bimodal sediments shows little variation with grain size and depends only on the mean grain size bf the mixture for strongly bimodal sediments ci increases with grain size an apparent result of a lateral segregation of the finer and coarser fractions on the bed surface that causes ci to deviate from size independence in the direction of unisize shields values a quantitative definition of mixture bimodality may be used to estimate the degree of mixture bimodality beyond which a substantial size dependence of ci is observed and to predict the variation of ci with grain size in bimodal sediments because properties of sediment grain size distributions other than bimodality appear to have little influence on ci the trends presented here for 14 unimodal and bimodal sediments may be quite general

on the behavior of internal waves in the wakes of storms abstract the rossby adjustment process in the wake of a storm is studied with a view to finding within the context of linear theory how wave dispersion in both the vertical and meridional directions spreads energy which is initially confined entirely to the mixed layer comparisons are made between three cases 1 a periodic storm on the f plane where dispersion is purely vertical 2 a bounded storm on the f plane and 3 a bounded storm centered 2700 km from the equator on an equatorial beta plane particular attention is paid to the initial rate of loss of energy from the mixed layer and some simple formulas which work very well in the cases studied are derived these show that the rate of loss goes up when the mixed layer depth is increased and also that the rate scales as the square of the wavenumber values of the rates are sufficient to provide a major source of energy for internal waves below the mixed layer the often observed tendency for phase lines to propagate upward is found in all case

unraveling bed slope from relative roughness in initial sediment motion understanding incipient sediment transport is crucial for predicting landscape evolution mitigating flood hazards and restoring riverine habitats observations show that the critical shields stress increases with increasing channel bed slope and proposed explanations for this counterintuitive finding include enhanced form drag from bed forms particle interlocking across the channel width and large bed sediment relative to flow depth relative roughness here we use scaled flume experiments with variable channel widths bed slopes and particle densities to separate these effects which otherwise covary in natural streams the critical shields stress increased with bed slope for both natural gravel s 2 65 g cm 3 and acrylic particles s 1 15 g cm 3 and adjusting channel width had no significant effect however the lighter acrylic particles required a threefold higher critical shields stress for mobilization relative to the natural gravel at a fixed slope which is unexpected because particle density is accounted for directly in the definition of shields stress a comparison with model predictions indicates that changes in local velocity and turbulence associated with increasing relative roughness for lighter materials are responsible for increasing the critical shields stress in our experiments these changes lead to concurrent changes in the hydraulic resistance and a nearly constant critical stream power value at initial motion increased relative roughness can explain much of the observed heightened critical shields stresses and reduced sediment transport rates in steep channels and also may bias paleohydraulic reconstructions in environments with exotic submerged densities such as iron ore pumice or ice clasts on titan

tropical cyclones cause caco3 undersaturation of coral reef seawater in a high co2 world 1 ocean acidification is the global decline in seawater ph and calcium carbonate caco3 saturation state due to the uptake of anthropogenic co2 by the world s oceans acidification impairs caco3 shell and skeleton construction by marine organisms coral reefs are particularly vulnerable as they are constructed by the caco3 skeletons of corals and other calcifiers we understand relatively little about how coral reefs will respond to ocean acidification in combination with other disturbances such as tropical cyclones seawater carbonate chemistry data collected from two reefs in the florida keys before during and after tropical storm isaac provide the most thorough data to date on how tropical cyclones affect the seawater co2 system of coral reefs tropical storm isaac caused both an immediate and prolonged decline in seawater ph aragonite saturation state was depressed by 1 0 for a full week after the storm impact based on current business as usual co2 emissions scenarios we show that tropical cyclones with high rainfall and runoff can cause periods of undersaturation 1 0 for high mg calcite and aragonite mineral phases at acidification levels before the end of this century week long periods of undersaturation occur for 18 mol high mg calcite after storms by the end of the century in a high co2 world caco3 undersaturation of coral reef seawater will occur as a result of even modest tropical cyclones the expected increase in the strength frequency and rainfall of the most severe tropical cyclones with climate change in combination with ocean acidification will negatively impact the structural persistence of coral reefs

a systematic analysis of eight decades of incipient motion studies with special reference to gravel bedded rivers data compiled from eight decades of incipient motion studies were used to calculate dimensionless critical shear stress values of the median grain size t c 50 calculated t c 50 values were stratified by initial motion definition median grain size type surface subsurface or laboratory mixture relative roughness and flow regime a traditional shields plot constructed from data that represent initial motion of the bed surface material reveals systematic methodological biases of incipient motion definition t c 50 values determined from reference bed load transport rates and from visual observation of grain motion define subparallel shields curves with the latter generally underlying the former values derived from competence functions define a separate but poorly developed field while theoretical values predict a wide range of generally higher stresses that likely represent instantaneous rather than time averaged critical shear stresses the available data indicate that for high critical boundary reynolds numbers and low relative roughnesses typical of gravel bedded rivers reference based and visually based studies have t c50 ranges of 0 052 0 086 and 0 030 0 073 respectively the apparent lack of a universal t 50 for gravel bedded rivers warrants great care in choosing defendable t c50 values for particular applications

discrete particle modeling of entrainment from flat uniformly sized sediment beds the stability of randomly deposited sediment beds is examined using a discrete particle model in which individual grains are represented by spheres the results indicate that the threshold shear stress for flat beds consisting of cohesionless uniformly sized grains cannot be adequately described by a single valued parameter rather it is best represented by a distribution of values physically this result stems from the localized heterogeneity in the arrangement of surface grains for uniformly sized beds geometric similarity exists such that the critical entrainment shear stress distributions scale directly with grain size a shields parameter of 0 06 is commonly used to define threshold conditions and it was found that this corresponds to a point on the distributions where approximately 1 4 by weight of the surface is mobile furthermore the analysis includes a comparison of the contributions of sheltering to variation in critical entrainment shear stress it was found that remote sheltering ind

spatial distribution and controlling factors of planktonic foraminifera in the modern western pacific abstract studies of the spatial distribution of living planktonic foraminifera in modern water columns are still lacking in the western pacific in this study 40 plankton tows at 8 stations were conducted focusing on the terminus of the north equatorial current nec and its two bifurcated branches in the western pacific the results show that planktonic foraminifera were in high abundance around the kuroshio current kc source region and the mindanao current mc system but in low abundance in the nec the planktonic foraminiferal assemblage was dominated by g sacculifer and g ruber with relative abundances of 44 0 and 27 3 respectively according to a cluster analysis of the results of seven stations the stations can be divided into three groups namely group nec group kc and group mc which displayed different features of planktonic foraminiferal assemblages the low abundance of planktonic foraminifera that characterized the nec stations may be induced by the thick mixed layer and deep thermocline nutricline in this region however stations in the kc region which also had thick mixed layers and deep thermoclines showed higher abundances of planktonic foraminifera than the nec stations this result was probably caused by the higher terrigenous input the planktonic foraminifera show the highest abundance at the mc stations which may be the result of existing upwelling conditions

effects of bed forms and large protruding grains on near bed flow hydraulics in low relative submergence conditions in mountain rivers bedforms large relatively immobile grains and bed texture and topographic variability can significantly alter local and reach averaged flow characteristics the low relative submergence of large immobile grains causes highly three dimensional flow fields that may not be represented by traditional shear stress flow velocity and turbulence intensity equations to explore the influence of large protruding grains and bedforms on flow properties we conducted a set of experiments in which we varied the relative submergence while holding the sediment transport capacity and upstream sediment supply constant flow and bed measurements were conducted at the beginning and end of each experiment to account for the absence or presence of bedforms respectively detailed information on the flow was obtained by combining our measurements with a 3d numerical model commonly used velocity profile equations only performed well at the reach scale when shallow flow effects and the roughness length of the relatively mobile sediment were considered however at the local scale large deviations from these profiles were observed and simple methods to estimate the spatial distribution of near bed shear stresses are likely to be inaccurate zones of high turbulent kinetic energy occurred near the water surface and were largely controlled by the immobile grains and plunging flow the reach averaged shear stress did not correlate to depth or slope as commonly assumed but instead was controlled by the relative boulder submergence and degree of plunging flow for accurate flow predictions in mountain rivers the effects of bedforms and large boulders must be considered

debris flow dominance of alluvial fans masked by runoff reworking and weathering arid alluvial fan aggradation is highly episodic and fans often comprise active and inactive sectors hence the morphology and texture of fan surfaces are partly determined by secondary processes of weathering and erosion in addition to primary processes of aggradation this introduces considerable uncertainty in the identification of formative processes of terrestrial and martian fans from aerial and satellite imagery the objectives of this study are i to develop a model to describe the sedimentological and morphological evolution of inactive fan surfaces in arid settings and ii to assess the relative importance of primary processes of aggradation and secondary processes of weathering and reworking for surface morphology and sedimentology and for the stratigraphic record we studied an alluvial fan characterized by a recently active sector and a long abandoned inactive sector along the coast of the hyperarid atacama desert here rates of primary geomorphic activity are exceptionally low because of extreme aridity while weathering rates are relatively high because of the effects of coastal fogs long term processes of fan aggradation and reworking were determined through sedimentological facies analysis of stratigraphic sections ground surveys for textural and morphological patterns at the fan surface were integrated with remote sensing by an unmanned airborne vehicle uav discharges and sediment transport capacities were calculated to estimate the efficiency of secondary runoff in reshaping the inactive fan sector stratigraphic sections reveal that the fan was dominantly aggraded by debris flows whereas surface morphology is dominated by debris flow signatures in the active sector and by weathering and runoff on the inactive sector on the latter rapid particle breakdown prevents the formation of a coarse desert pavement furthermore relatively frequent local runoff events erode proximal debris flow channels on the inactive sector to form local lag deposits and accumulate fine sediment in low gradient distal channels forming a well developed drainage pattern that would suggest a runoff origin from aerial images nevertheless reworking is very superficial and barely preserved in the stratigraphic record this implies that fans on earth and mars that formed dominantly by sporadic mass flows may be masked by a surface morphology related to other processes

neogloboquadrina pachyderma sinistral coiling as paleoceanographic tracers in polar oceans evidence from northeast water polynya plankton tows sediment traps and surface sediments the abundance and chemistry of the planktonic foraminifera neogloboquadrina pachyderma sinistral coiling have long been used as tools for monitoring polar surface ocean changes and for correlating these changes to atmospheric and thermohaline circulation fluctuations however due to its remote habitat very little is known about how modern n pachyderma s respond to changing environmental conditions in the polar seas modern samples of n pachyderma s from the northeast water polynya provide a means for studying how environmental conditions affect the vertical distribution and chemistry of this species highest abundances of n pachyderma s were associated with the chlorophyll maximum in the surface 20 80 m where they are exploiting their primary food source evidence suggests that the addition of a calcite crust modifies the calcite tests of some n pachyderma s between 50 and 200 m increasing shell density and modifying shell chemistry the shell mass of encrusted forms is 3 4 times greater than the nonencrusted forms between 50 and 200 m the oxygen isotope composition of n pachyderma s shells increase by 1 5 in response to local water column gradients the 13c values of n pachyderma s are basically invariant with depth in this region are consistently 1 0 depleted in comparison with the 13c for equilibrium calcite and remain basically constant during the shell thickening process mass balance calculations suggest that encrustation occurs at all depths but abundance counts suggest that the process occurs mostly at the depth of the main pycnocline sediment fluxes of n pachyderma s occur during a 2 week bloom event and decrease to almost zero below complete ice cover the decoupling of the processes controlling abundances and shell chemistry explain the discrepancies between transfer function and isotopically derived paleotemperature estimates of surface conditions in some oceanic settings the ability of 18o to record surface ocean conditions will depend on vertical water column gradients as evidenced by the differences in core top calibrations between the north and south atlantic

measurement of fluctuating pressures on coarse bed material bed protections are usually characterized by low mobility transport conditions and nonequilibrium turbulence profiles as the present knowledge of the influence of turbulence on stability of cover layer units is minimal an in depth investigation was undertaken regarding the influence of turbulence on the stability of rough granular beds detailed measurements of fluctuating pressures on a bed element are used to evaluate certain concepts that are often used in modeling the entrainment of bed material from hydraulically rough beds three pressure transducers are placed in a cube that is part of a rough granular bed under open channel flow and velocities are measured using laser doppler velocimetry the measurements show that the magnitude of the fluctuating pressure at a certain point of the cube is a function of the exposure relative to the stones upstream of the cube a quadrant analysis reveals that the drag force is not only directly dependent on the horizontal near bed velocity but on the vertical velocity as well further the effect of small scale eddies shedding from the stone during large scale increases of longitudinal velocity is shown the fact that large scale velocity fluctuations create a large part of the pressure or force variance indicates that downstream of a roughness transition these fluctuations have to be taken into account in order to evaluate the stability of the bed

seasonal succession vertical distribution and dissolution of planktonic foraminifera along the subarctic front implications for paleoceanographic reconstruction in the northwestern pacific abstract the regional spatial and depth distribution of planktonic foraminifera were studied through sediment trap observations at two stations stations wct 5 about 41 n 150 e and wct 6 about 42 n 155 e along the subarctic front in the northwestern pacific ocean the sediment traps were moored at 1000 and 4500 m depths at station wct 5 and 1091 2051 and 4871 m depths at station wct 6 the samples were collected from 17 august 1998 to 10 august 1999 at station wct 5 and from 15 august 1999 to 6 august 2000 at wct 6 at station wct 5 two distinct annual periods of increased total foraminiferal and species production were evident the period of highest production was in autumn with a secondary period in early summer at station wct 6 high total foraminiferal shell fluxes occurred in april may and september october the april may spring bloom of planktonic foraminifera apparently began each year as the sea surface temperature sst increased after winter and the decrease of thickness of the mixed water layer during june july in every year following the cessation of bloom the most common foraminiferal species in the study region were globigerina quinqueloba neogloboquadrina pachyderma neogloboquadrina dutertrei neogloboquadrina incompta globigerinita glutinata globigerina bulloides globigerina falconensis globorotalia theyeri globorotalia scitula and globigerinella calida foraminiferal fluxes displayed a distinct seasonality at all trap depths at both stations at station wct 5 in 1998 1999 foraminiferal species were scarce in the surface water during spring and summer and the dominant foraminiferal species were most productive during winter and autumn at station wct 6 the dominant foraminiferal species were most productive during late winter to spring and all species showed a peak in middle spring may a comparison of seasonal patterns of dominant foraminiferal species between the northwestern and northeastern pacific demonstrated that foraminiferal productivity was a good proxy for sea surface temperature and mixing of water column significant dissolution of foraminiferal tests was evident in the deepwater column and was used to estimate the foraminiferal lysocline depth 4500 m in the northeastern pacific basin

friction angle measurements on a naturally formed gravel streambed implications for critical boundary shear stress we report the first measurements of friction angles for a naturally formed gravel streambed for a given test grain size placed on a bed surface friction angles varied from 10o to over 100o friction angle distributions can be expressed as a function of test grain size median bed grain size and bed sorting parameter friction angles decrease with increasing grain size relative to the median bed grain size and are a systematic function of sorting with lower friction angles associated with poorer sorting the probability distributions of critical shear stress for different grain sizes on a given bed surface as calculated from our friction angle data show a common origin but otherwise diverge with larger grains having narrower and lower ranges of critical shear stresses the potential mobility of a grain as defined by its probability distribution of critical shear stress may be overestimated for larger grains in this analysis because our calculations do not take into account the effects of grain burial and altered near bed flow fields

initiation and flow conditions of contemporary flows in martian gullies understanding the initial and flow conditions of contemporary flows in martian gullies generally believed to be triggered and fluidized by co2 sublimation is crucial for deciphering climate conditions needed to trigger and sustain them we employ the ramms rapid mass movement simulation debris flow and avalanche model to back calculate initial and flow conditions of recent flows in three gullies in hale crater we infer minimum release depths of 1 0 1 5 m and initial release volumes of 100 200 m3 entrainment leads to final flow volumes that are 2 5 5 5 times larger than initially released and entrainment is found necessary to match the observed flow deposits simulated mean cross channel flow velocities decrease from 3 4 m s 1 to 1 m s 1 from release area to flow terminus while flow depths generally decrease from 0 5 1 m to 0 1 0 2 m the mean cross channel erosion depth and deposition thicknesses are 0 1 0 3 m back calculated dry coulomb friction ranges from 0 1 to 0 25 and viscous turbulent friction between 100 200 m s 2 which are values similar to those of granular debris flows on earth these results suggest that recent flows in gullies are fluidized to a similar degree as are granular debris flows on earth using a novel model for mass flow fluidization by co2 sublimation we are able to show that under martian atmospheric conditions very small volumetric fractions of co2 of 1 within mass flows may indeed yield sufficiently large gas fluxes to cause fluidization and enhance flow mobility

atmospheric sensitivity to sst near the kuroshio extension during the extratropical transition of typhoon tokage abstract it is hypothesized that the tropical to extratropical transition of a cyclone in the western north pacific can be sensitive to the underlying sea surface temperature sst distribution this hypothesis was tested through a case study of typhoon tokage using a series of high resolution simulations by the weather research forecast wrf numerical weather prediction model simulations were carried out for a control sst distribution and for sst distributions with imposed warm and cold perturbations of 1 5 c maximum amplitude in the vicinity of the kuroshio extension the simulations with the warm sst perturbation yielded a cyclone slightly weaker than in the control sst case about 2 days after transition in contrast the cold sst perturbation case yielded a cyclone with a central pressure 10 hpa lower than in the control case at the same point in the storm s life cycle apparently due to its more northward track and hence closer proximity to an approaching upper level trough and perhaps in associati

planktonic foraminiferal fluxes in the santa barbara basin response to seasonal and interannual hydrographic changes results of a three year time series sediment trap experiment in the santa barbara basin indicate linkages between water column dynamics and variations in plankton fluxes on both seasonal and interannual time scales the two week collection interval utilized for this study allows evaluation of high frequency changes in the production and flux of planktonic foraminifera which are compared to those of siliceous microorganisms diatoms radiolaria and silicoflagellates annual hydrographic conditions in santa barbara basin are influenced by seasonal changes in insolation the wind field and source waters this study includes periods of weak to moderate el nino conditions followed by a transitional period to a non el nino state planktonic foraminiferal fluxes and species turnover are related to seasonal and interannual changes in source waters and water column conditions globigerina bulloides g quinqueloba and neogloboquadrina pachyderma dextral dominate the planktonic foraminiferal population in this location and are present throughout the year globigerina bulloides and g quinqueloba have similar flux patterns and highest fluxes occur in association with diatom blooms the flux patterns of g bulloides and g quinqueloba in general are inversely related to that of n pachyderma dextral globigerina quinqueloba seems to respond earlier to the onset of upwelling than g bulloides three temperature limited species neogloboquadrina dutertrei orbulina universa and globigerinoides ruber are present in lower numbers and show more restricted seasonal ranges in the thermal regime of the santa barbara basin n dutertrei like o universa disappears during upwelling neogloboquadrina dutertrei occurs in highest abundance when the water column is thermally stratified and there is a well developed deep chlorophyll maximum increased fluxes of globigerinoi ruber the most thermally restricted of the dominant species in the basin are associated with the presence of warm oceanic diatoms and warm water radiolarians total planktonic foraminiferal fluxes were lower in 1995 than during the previous two years which were characterized by el nino conditions

regional and interannual productivity of biogenic components and planktonic foraminiferal fluxes in the northwestern pacific basin abstract time series sediment trap experiments at subtropical wct 1 and subarctic wct 2 stations in the northwestern pacific indicate seasonal latitudinal and depth variations in total particulate biogenic and foraminiferal fluxes at the subtropical station the average total mass flux was 19 4 mg m 2 day 1 in the shallow trap 1060 m and 21 5 26 1 mg m 2 day 1 in the deep trap 3930 m during the sampling period at subarctic station these values were 91 5 176 9 mg m 2 day 1 in the shallow and 68 6 112 3 mg m 2 day 1 in the deep trap we recognized 12 and 15 planktonic foraminiferal species at station wct 1 and station wct 2 respectively the planktonic foraminiferal flux and species turnover are related to seasonal and interannual changes in source water and water column conditions at both stations at station wct 1 the highest flux was recorded during the summer with a peak in mid to late june associated with similar flux patterns of the dominant species globigerinoides ruber and globigerinita glutinata the total flux of foraminiferal tests at the shallow and deep traps is similar in numbers and magnitude at station wct 2 the peaks of total flux of foraminiferal tests at the two trap depths differ in number and their magnitude in the deep trap is almost half of that in the shallow trap a distinctive seasonal pattern occurred in the shallow and the deep trap with a peak in total foraminiferal flux in mid june to mid july globigerina quinqueloba neogloboquadrina pachyderma and neogloboquadrina dutertrei dominate the planktonic population throughout the year subtropical station wct 1 was characterized by low total foraminiferal fluxes and low total mass flux which is dominated by calcium carbonate and depleted in opal whereas high foraminiferal fluxes and a high total mass flux dominated by high biogenic opal and less calcium carbonate and organic matter characterize subarctic station wct 2 the foraminiferal carbonate that reaches the seafloor accounts for an average 20 27 and 22 23 of the total calcium carbonate at station wct 1 and station wct 2 respectively the primary reason for the difference in flux at both stations thus lies in the different contributions of siliceous and calcareous planktonic assemblages the seasonal variation in biogenic particulate flux at both stations implies that temporal changes in biological productivity are governed by large scale seasonal climatic variability and local hydrography

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

stochastic prediction of sediment transport in sand gravel bed rivers classical deterministic bedload transport predictors are applied to sand gravel bed rivers the turbulent bed shear stress is modeled according to a probability distribution to obtain realistic bedload transport rates at incipient motion in extending the predictors to stochastic predictors for nonuniform sediment many parameters that represent near bed turbulence and the particle size distribution must be chosen the parameters that give realistic results are chosen by analyzing the results of a new experimental flume dataset with relatively large water depths choosing other combinations of parameters may give equal total bedload transport rates but at the cost of large errors in fractional transport rates attention is given to the hiding exposure phenomenon and a hindrance effect related to nonuni form sediment validation based on two independent field datasets shows that successful predictions of particle sizes near the threshold for motion are feasible using the stochastic approach while the deterministic approach gives successful predictions well above incipient motion

a perpetually running enso in the pliocene abstract difficulties remain with theoretical explanations of the apparent reduced zonal sea surface temperature gradient in the tropical pacific of the pliocene one favored hypothesis is that it was a permanent el nino state with the warm phase of enso remaining fixed over millions of years here an alternative is suggested that there was a perpetually running enso with a shorter return time than is observed today and that the apparently reduced zonal gradient is an alias rectification of a high frequency signal governed by the growth patterns of the foraminifera used to provide proxy temperatures the hypothesis is probably testable in the modern ocean with comparatively modest measurements of foraminifera behavior in time

evaluation of bed load transport subject to high shear stress fluctuations 1 many formulas available in the literature for computing sediment transport rates are often expressed in terms of time mean variables such as time mean bed shear stress or flow velocity while effects of turbulence intensity e g bed shear stress fluctuation on sediment transport were seldom considered this may be due to the fact that turbulence fluctuation is relatively limited in laboratory open channel flows which are often used for conducting sediment transport experiments however turbulence intensity could be markedly enhanced in practice this note presents an analytical method to compute bed load transport by including effects of fluctuations in the bed shear stress the analytical results obtained show that the transport rate enhanced by turbulence can be expressed as a simple function of the relative fluctuation of the bed shear stress the results are also verified using data that were collected recently from specifically designed laboratory experiments the present analysis is applicable largely for the condition of a flat bed that is comprised of uniform sand particles subject to unidirectional flows

the inertial chimney the near inertial energy drainage from the ocean surface to the deep layer a three dimensional primitive equation numerical model is used to study the behavior of near inertial waves generated by surface wind stress on an plane the model is fixed depth with a rigid lid on the surface and is horizontally periodic this study shows the behaviors of the wind generated near inertial waves for four different eddies 1 a subtropical cold core eddy 2 a subtropical warm core eddy 3 a california subsurface warm core eddy and 4 the gulf stream warm core ring the mean secondary circulation generated by the wind eddy interaction has magnitude to comparable to that of the ekman current and its characteristics are determined by the relative angle between wind and current the propagation characteristics of near inertial waves are quite different depending upon the sign of the relative vorticity in a cyclonic eddy near inertial wave propagation is outward from the core of the eddy the propagation direction in an anticyclonic eddy is downward and toward the core vertically propagating waves inside the eddy are trapped above a critical layer and slowly dissipated by parameterized viscous effects the model shows that anticyclones efficiently drain near inertial energy from the surface to the deep layer below the thermocline