enhanced turbulence and energy dissipation at ocean fronts the ocean surface boundary layer mediates air sea exchange in the classical paradigm and in current climate models its turbulence is driven by atmospheric forcing observations at a 1 kilometer wide front within the kuroshio current indicate that the rate of energy dissipation within the boundary layer is enhanced by one to two orders of magnitude suggesting that the front rather than the atmospheric forcing supplied the energy for the turbulence the data quantitatively support the hypothesis that winds aligned with the frontal velocity catalyzed a release of energy from the front to the turbulence the resulting boundary layer is stratified in contrast to the classically well mixed layer these effects will be strongest at the intense fronts found in the kuroshio current the gulf stream and the antarctic circumpolar current all of which are key players in the climate system

near surface dynamical structure of the kuroshio extension 1 lagrangian data from 657 svp drifters cnes aviso archiving validation and interpretation of satellite oceanographic data time variable satellite altimeter sea level anomaly and levitus 98 hydrographic data are used to develop 0 25 spatial resolution maps of the mean and eddy circulations in the northwestern pacific during the 1990s drifter velocities at 15 m depth and 200 m temperature data clearly indicate in the kuroshio extension ke jet two prominent meanders that culminate in a 300 km northward deflection east of the shatsky rise at 160 e the interannual trends of aviso mesoscale variance are absent along the path of the meandering ke jet three anticyclonic recirculations can be identified south or southeast of the kuroshio the southernmost around daito island being a new discovery about 3 of the drifters with drogues attached crossed the kuroshio front the aviso currents are correlated at 0 8 with drifter geostrophic velocity the aviso geostrophic currents are adjusted in amplitude to the contemporaneous drifter observations and are further used to compute an unbiased mean geostrophic circulation and the quasi geostrophic reynolds stresses in the ke region the principal axes of the eddy reynolds stresses are oriented along the unbiased mean velocity vectors within the meandering ke jet the time mean horizontal momentum balance that includes both the mean and eddy momentum convergences is used to compute absolute sea level map and its uncertainty at 145 e the 2000 m depth absolute dynamic height referenced to the sea level reveals a heretofore unknown 70 dynamic cm drop from 25 to 42 n

seasonal changes in beach morphology along the sheltered coastline of perth western australia abstract seasonal change in beach morphology is traditionally ascribed to a variation in the incident wave energy level with calm conditions in summer resulting in wide beaches with pronounced subaerial berms and energetic conditions in winter causing narrow beaches with nearshore bar morphology the coastline of perth western australia is characterised by a large seasonal variation in the incident wave height and local beaches exhibit a distinct seasonal change in morphology however these morphological changes are better explained by a seasonal reversal in the littoral drift direction than by variations in the incident wave energy conditions in summer when northward sediment transport prevails due to sea breeze activity beaches located south of coastal structures headlands or rocky outcrops become wider due to the accumulation of sediment against the obstacle these beaches will subsequently erode in winter during storms when the longshore sediment transport is toward the south in contrast beaches located north of obstacles will become narrower during summer and wider during winter the usefulness of the dimensionless fall velocity h b w s t where hb is the breaker height ws is the sediment fall velocity and t is the wave period as a predictor of presence absence of bar morphology and beach type was investigated it was found that fluctuates around the threshold of bar formation 1 5 2 over a variety of time scales daily weekly and seasonally these temporal variations in in conjunction with the relatively low wave energy level that characterises the coast negates the development of beach and nearshore morphology that is in equilibrium with the hydrodynamic conditions as a result bar occurrence and beach type can not be readily predicted using along the perth coast

uranium lead dates from the central gneiss complex and ecstall pluton prince rupert map area british columbia uranium lead dates for nine zircon fractions from six rock samples of central gneiss complex cgc are concordant between 65 and 85 ma two fractions from a sample near the eastern edge of the cgc give discordant u pb dates between 108 and 171 ma but analytical uncertainties and geological complexities prohibit meaningful interpretation two fractions from two samples from the ecstall pluton give concordant u pb dates of about 98 4 ma and date the emplacement of the ecstall pluton the concordant cgc dates indicate late cretaceous to early tertiary peak metamorphism granulite and amphibolite facies of the cgc east of work channel lineament this contrasts with a slightly older mid cretaceous peak metamorphism west of work channel lineament inferred from the synmetamorphic nature of the ecstall pluton

seasonal variation and instability nature of the north pacific subtropical countercurrent and the hawaiian lee countercurrent 1 the relation between baroclinic instability of the north pacific subtropical countercurrent stcc and the hawaiian lee countercurrent hlcc and seasonal evolution of mesoscale sea surface height ssh variability was investigated by using historical hydrographic data and altimeter derived ssh anomaly data during 1992 2000 the annual and monthly mean dynamic height climatologies show two robust eastward flowing countercurrents the stcc extends typically along 24 n from 130 e to 160 w and slightly shifts to the north as it flows toward the east and the hlcc is located typically along 20 n and extends from about 150 e to just west of the hawaiian islands seasonal variations of the stcc in the western north pacific and the hlcc west of the hawaiian island where the eddy variability is relatively larger than the background were quite different the stcc hlcc is strong in winter summer to summer winter and weak in fall spring in contrast seasonal evolution of mesoscale ssh variability has almost the same cycle in the two countercurrent regions the eddy kinetic energy eke is a maximum in spring and a minimum in fall the dominant zonal scales are shortest in late winter and become longer with time a linear quasigeostrophic stability analysis using a three layer model indicates that instability properties are very similar between the two countercurrent regions the stcc and the hlcc become baroclinically more unstable during winter and late fall to winter respectively due to strong vertical velocity shear and weak stratification between the stcc hlcc and underlying westward flow and the most unstable wave during this season has an e folding timescale of about 2 3 months and a zonal wavelength of about 300 400 km the same behavior of the seasonal evolution of the mesoscale variability in the two countercurrent regions is a manifestation of these similarities in terms of increasing nonlinearity of the unstable waves and an inverse cascade of the eddy energy we discussed generation processes of the mesoscale ssh disturbances

eddies in the red sea a statistical and dynamical study sea level anomaly sla data spanning 1992 2012 were analyzed to study the statistical properties of eddies in the red sea an algorithm that identifies winding angles was employed to detect 4998 eddies propagating along 938 unique eddy tracks statistics suggest that eddies are generated across the entire red sea but that they are prevalent in certain regions a high number of eddies is found in the central basin between 18 n and 24 n more than 87 of the detected eddies have a radius ranging from 50 to 135 km both the intensity and relative vorticity scale of these eddies decrease as the eddy radii increase the averaged eddy lifespan is approximately 6 weeks aes and cyclonic eddies ces have different deformation features and those with stronger intensities are less deformed and more circular analysis of long lived eddies suggests that they are likely to appear in the central basin with aes tending to move northward in addition their eddy kinetic energy eke increases gradually throughout their lifespans the annual cycles of ces and aes differ although both exhibit significant seasonal cycles of intensity with the winter and summer peaks appearing in february and august respectively the seasonal cycle of eke is negatively correlated with stratification but positively correlated with vertical shear of horizontal velocity and eddy growth rate suggesting that the generation of baroclinic instability is responsible for the activities of eddies in the red sea

constructal view of scaling laws of river basins abstract river basins are examples of naturally organized flow architectures whose scaling properties have been noticed long ago based on data of geometric characteristics horton horton r e 1932 drainage basin characteristics eos trans agu 13 350 361 hack hack j t 1957 studies of longitudinal profiles in virginia and maryland usgs professional papers 294 b washington dc pp 46 97 and melton melton m a 1958 correlation structure of morphometric properties of drainage systems and their controlling agents j of geology 66 35 56 proposed scaling laws that are considered to describe rather accurately the actual river basins what we show here is that these scaling laws can be anticipated based on constructal theory which views the pathways by which drainage networks develop in a basin not as the result of chance but as flow architectures that originate naturally as the result of minimization of the overall resistance to flow constructal law

seasonal mesoscale and submesoscale eddy variability along the north pacific subtropical countercurrent abstractlocated at the center of the western north pacific subtropical gyre the subtropical countercurrent stcc is not only abundant in mesoscale eddies but also exhibits prominent submesoscale eddy features output from a high resolution ogcm simulation and a gridded satellite altimetry product are analyzed to contrast the seasonal stcc variability in the mesoscale versus submesoscale ranges resolving the eddy scales of 150 km the altimetry product reveals that the stcc eddy kinetic energy and rms vorticity have a seasonal maximum in may and april respectively a weak positive vorticity skewness without seasonal dependence and an inverse forward kinetic energy cascade for wavelengths larger shorter than 250 km in contrast the submesoscale resolving ogcm simulation detects that the stcc eddy kinetic energy and rms vorticity both appear in march a large positive vorticity skewness with strong seasonality and an intense inverse kinetic energy cascade whose short wave cutoff migrates seaso

loop current and deep eddies abstract in contrast to the loop current and rings much less is known about deep eddies deeper than 1000 m of the gulf of mexico in this paper results from a high resolution numerical model of the gulf are analyzed to explain their origin and how they excite topographic rossby waves trws that disperse energy to the northern slopes of the gulf it is shown that north of campeche bank is a fertile ground for the growth of deep cyclones by baroclinic instability of the loop current the cyclones have horizontal vertical scales of about 100 km 1000 2000 m and swirl speeds 0 3 m s 1 the subsequent development of these cyclones consists of two modes a and b mode a cyclones evolve into the relatively well known frontal eddies that propagate around the loop current mode a cyclone can amplify off the west florida slope and cause the loop current to develop a neck that sometimes leads to shedding of a ring this process is shown to be the loop current s dominant mode of upper to deep variability

subsurface subtropical fronts of the north pacific as inherent boundaries in the ventilated thermocline the two subsurface temperature density fronts and the accompanying eastward currents in the central and southern part of the north pacific subtropical gyre are identified using the repeat hydrographic sections in the western part of the gyre and the sections over the whole gyre from the world ocean circulation experiment woce hydrographic program whp the northern eastward current corresponds to what has been known as the subtropical countercurrent stcc the countercurrent front is located typically near 24 8n and extends from the western boundary approximately to the international date line the previous suggestion that the stcc is located at the southern edge of north pacific subtropical mode water stmw is confirmed the front appears as the southern boundary of the lower potential vorticity pv apparent oxygen utilization aou waters on the isopycnals within the stmw layer the southern eastward current corresponds to what was recognized earlier but has not been documented in detail the southern countercurrent front is located near 188n west of the date line but shifts to the north east of the date line its eastern limit is around 165 8 wa t 258n the southern front corresponds to the southern boundary of the lower pv aou waters on the isopycnal surfaces of the wide su range including those of north pacific central mode water cmw while cmw seems to contribute largely to this low pv aou layer the contribution from other waters is still significant judging from the associated pv aou features in the thermocline both fronts can be regarded as inherent boundaries in the ventilated thermocline dividing the regions ventilated to distinctive degrees correspondence between the observational features of the countercurrents fronts and some of the previously proposed theories concerning the stcc are discussed

the influence of beach porosity on wave uprush and backwash abstract packwood a r 1983 the influence of beach porosity on wave uprush and backwash coastal eng 7 29 40 a numerical model is described to calculate the influence of a porous bed on the run up of a bore on a gently sloping sandy beach it is shown that fine medium grade sands have very little effect in the run up phase significant differences between impermeable and porous bed solutions are found in the backwash which might explain certain sand erosion and deposition phenomena

geological control of beach morphodynamic state the concept of beach morphodynamic states has achieved widespread acceptance in the coastal geological literature since its inception in the mid 1980s and expansion in the 1990s much of the pioneering work was undertaken in australia under a range of environmental conditions in microtidal environments and a close empirical relationship between beach 3 dimensional morphology and the dean s parameter h b wst was established subsequently the relative tidal range parameter h b tr was extended to beaches of all tidal ranges in this paper observations are presented from 25 beaches around the north coast of ireland these beaches exist on an environmental gradient that encompasses marked tidal and wave energy variability micro to macrotidal and low to high wave energy each beach was visually categorised into one of several established beach states described in the literature on the basis of field observations for each beach the rtr and dean s parameter were calculated for the immediately antecedent period and used to predict the beach state using published relationships observed and predicted beach states were then compared comparison of observed and predicted beach states showed that while beaches with observed dissipative morphology typically matched the expected criteria most other beach states did not lack of agreement between predicted and observed beach states has been reported elsewhere and attributed to failings in the rtr and dean s parameter in addition this study identifies geological factors as important constraints on actual beach state in the majority of beaches studied inherited geological factors appear to be more important determinants of beach morphology than contemporary dynamics c 2005 elsevier b v all rights reserved

seasonal exchanges of the kuroshio and shelf waters and their impacts on the shelf currents of the east china sea previous in situ observations and modeling studies have indicated that through mass and momentum exchanges across the shelf edge the kuroshio can significantly influence the shelf currents of the east china sea ecs here instead of localized observations this study uses 25yr of drifter data supported by satellite and other data to identify seasonal cross shelf exchanges along the entire shelf edge the authors show that kuroshiomeandersonshorefromfalltowinterandoffshorefromspringtosummer withthelargestamplitude northeast of taiwan the influence is limited to the shelf edge when the kuroshio meanders offshore in spring and summer by contrast strong onshelf intrusions and cross shelf exchanges occur when the kuroshio meanders onshore in fall and winter drifters intrude onshelf northeast of taiwan and spread as far north as 308n against the strong northeasterly wind the forcing on the shelf is identified as a northward downsloping of the sea level that is steepest north of taiwan at 258 288n but which is 3 times weaker farther north the vorticity budget computed from a numerical model indicates that intrusion during fall andwinter is primarily a result of balancebetweenonshelfadvectionofambientpotentialvorticityandvorticityproductionbythealong isobath pressure gradient acting on the changing mass of water column across the continental slope

groin impacts on updrift morphology physical and numerical study abstract groins interfere with coastal dynamics and sediment transport leading to sediments accumulation at the updrift side while at downdrift the erosive process is anticipated due to the lack of sediments to improve numerical modeling capacity to simulate the groins impacts it is necessary to totally understand the shoreline evolution along time and its relationship with the cross shore profiles shape the main goal of this work was to analyze and compare the performance of physical and numerical studies on evaluating the evolution of updrift cross shore profiles geometry and shoreline position after the construction of a groin this study analyzed a coastal stretch updrift of the groin at a prototype and model scales considering the analytical formulation of pelnard considere the numerical model ltc long term configuration and the laboratory tests the laboratory tested scenario was designed with the aim to gather results which could be analyzed and compared with numerical simulations from ltc coelho 2005 allowing its improvement and with the pelnard considere 1956 analytical formulation both at model scale the developed study shows an important difference between ltc and pelnard considere 1956 approaches because the analytical solution for the shoreline in equilibrium does not include the wave refraction effects over the updated bathymetry ltc observed trend of the equilibrium shoreline is not parallel to the initial shoreline and this behavior was confirmed in the laboratory tests it was also observed that the sediment transport capacity has very small impact on the ltc shoreline configuration despite the refraction effects over the updated bathymetries along time the profile shape obtained in laboratory includes bed forms difficult to reproduce in long term numerical modeling evaluation of cross shore profiles because ltc transversal behavior is only based on geometrical considerations and does not represent cross shore sediment transport and its impact on profile geometry

relative motions between oceanic plates of the pacific basin appendix tables are available with entire article on microfiche order from american geophysical union 2000 florida avenue n w washington d c 20009 document b84 012 2 50 payment must accompany order relative motion poles describing the displacement histories between the pacific plate and once adjacent oceanic plates farallon kula izanagi i izanagi ii and phoenix were derived for the late mesozoic and cenozoic eras because fracture zone and magnetic anomaly data are generally available from the pacific plate but not from adjacent plates a new method of analysis for onesided data was required this analysis produced stage poles and rates of relative plate motion and estimates of their confidence regions the following are the main conclusions drawn from our analysis 1 for time intervals of the order of 107 years termed stages relative motion poles for plate pairs remained nearly fixed between stages shifts in poles were commonly both large and abrupt within stages rates of plate motion were commonly observed to change markedly indicating that plates changed speed more frequently than they changed direction 2 the relative motions of all of the plates analyzed changed at about chron m11 135 ma chron 34 85 ma and chron 25 56 ma 3 during the early cretaceous there were five oceanic plates in the pacific basin rather than the four recognized by previous workers 4 to determine the number of farallon plates that existed to the east of the pacific plate during the time interval from chron 34 85 ma to chron 25 56 ma fracture zones and magnetic anomalies that record pacific farallon spreading from the northern central and southern pacific plate were analyzed separately and collectively the analysis shows that a single pacific farallon relative motion pole and a single rate are consistent with all of the data 5 spreading rates along the pacific kula ridge decreased markedly between chrons 32b and 25 72 56 ma probably in response to the arrival of buoyant kula lithosphere at a subduction zone northwest of the bering sea 6 soon after chron 25 56 ma a major reorganization is recorded along the pacific farallon boundary the kula farallon boundary is also thought to have changed during this reorganization 7 kula pacific anomalies north of anomaly 25 are modeled by assuming continued kula pacific spreading after chron 25 56 ma 8 probably by chron 18 43 ma pacific kula spreading had ceased and the kula farallon ridge system had evolved into alignment with the pacific farallon spreading direction however the timing of these events is uncertain because pacific kula data younger than chron 25 56 ma are sparse

sand size versus beachface slope an explanation based on the constructal law article i nfo article history the relationship between beachface slope and sand grain size has been established based on multiple observations of beach characteristics in many parts of the world we show that this observational result may be understood in the light of the constructal law bejan 1997 a model of wave run up and run down along the beachface swash was developed to account for superficial flows together with flows through the porous sand bed of average porosity 0 35 the permeability of which may be related to grain diameter and sphericity 0 9 for sand grains through the kozeny carman equation then by using the constructal law we minimized the time for completing a swash cycle under fixed wave height and sand grain diameter as the result a relationship involving sand grain size beachface slope and open ocean wave height has been obtained and then discussed and validated against experimental data in addition this relationship has also been used to illuminate beachface dynamic processes namely the reshaping of sandy beachfaces in response to changes in wave height though the model used in this work may be improved further the results appear to show as with other natural systems that beachface morphing in time may be understood based on a unifying principle the constructal law

high and low k granites and adakites at a palaeoproterozoic plate boundary in northwestern australia the lamboo complex is one of several palaeoproterozoic terrains in northern australia that is intruded by high k i type granites the oldest granites in the complex consist of the high k 1865 1850 ma paperbark supersuite with initial e nd values between 2 7 and 4 0 tonalite sheets of the c 1850 ma dougalls suite have high al 2 o 3 na 2 o sr sr y and la yb and low y and hree and initial e nd values between 1 4 and 0 7 the rocks have compositions similar to adakites that form by melting of mafic rocks in the deep crust with garnet in the residue granites of the 1835 1805 ma sally downs supersuite range from high k types through to crustally derived adakites all with initial e nd values between 0 1 and 1 2 the two supersuites and the dougalls suite were intruded into different tectonic settings previously all of the granites in the lamboo complex were interpreted as partial melts of a chemically and isotopically uniform underplate beneath a rifted archaean craton however their spatial and temporal distribution and their varied compositions are best explained by large scale horizontal plate motions and subduction of oceanic crust

three subtropical fronts in the north pacific observational evidence for mode water induced subsurface frontogenesis 1 subsurface fronts in the subtropical north pacific were investigated by constructing a high resolution temperature climatology three distinct subtropical fronts stfs are identified which are the southern northern and eastern stfs according to their relative geographical locations the southern stf extends along 19 21 n west of the dateline while the northern and eastern stfs appear along 21 24 n and 26 n in the western and central subtropical gyre respectively our analysis showed that each of these stfs is associated with large negative meridional potential vorticity pv gradient in the thermocline below the front the northern stf is located on the southern edge of the kuroshio recirculation where the negative pv gradient occurs within a narrow density range and is maintained by the low pv core of the subtropical mode water stmw on the other hand the negative pv gradient at the eastern and southern stfs spans over a wide density range the eastern stf forms near the center axis of the subtropical gyre north of which the upper and lower portions of the central mode water cmw converge forming a thick low pv pool that maintains the negative pv gradient on the front similarly at the southern stf the negative pv gradient is due to a low pv pool to the north with the southernmost portion of the stmw stacked above the upper cmw advected from the central subtropical gyre it is concluded that the mode waters are essential for the north pacific stfs

exploiting remote imagery in an embayed sandy beach for the validation of a runup model framework storm surge and wave runup are key determinants of the potential for beach overwashing during storm events however the prediction and quantification of wave runup on embayed beaches is strongly influenced by particular characteristics e g irregular morphology low tides absence of swell etc which differ from those on open beaches and have rarely been investigated in literature in the present paper a model framework aimed at predicting wave induced runup on an embayed sandy beach is validated by means of measurements derived from a video monitoring station recently installed in south italy during two storm events in 2016 the numerical approach employs meteocean forecasted waves within swan and swash models in both 2 d and 1 d mode the combination of multibeam and d rtk surveys with unmanned aerial vehicle uav imagery provides high resolution depth grid m 0 015 particularly required in shallow waters where wave hydrodynamics is highly influenced by the bottom the results show and discuss the agreement between video measurements and 2 d predictions of runup a sensitivity analysis of the manningfls roughness factor is needed in 1 d simulations the accuracy of the empirical formulas in predicting wave runup in an embayed beach is also investigated showing mainly an overestimation of the observations

spatiotemporal variability of the global ocean internal processes inferred from satellite observations abstractusing a new analysis tool namely multiscale window transform mwt and the mwt based theory of canonical transfer this study investigates the spatiotemporal variations of the nonlinear

the role of swash infiltration in determining the beachface gradient a numerical study on sand and gravel beaches the increase of the gradient of the beachface with increasing sediment size has been attributed to swash infiltration the present study uses a process based numerical model to examine in detail the role of swash infiltration in determining the beachface gradient it is found that swash infiltration increases the onshore asymmetry in the swash flow thereby enhancing onshore sediment transport and resulting in relatively steep beachface gradients however the accretionary effects of swash infiltration are only evident when the rate of infiltration is sufficiently large i e when the total infiltration volume over a wave cycle exceeds c 2 of the uprush volume this threshold is attained when the hydraulic conductivity exceeds 1 cm s which is approximately equivalent to a grain size coarser than 1 5 mm this finding suggests that the correlation between beachface gradient and sediment size observed on sandy beaches is not due to enhanced swash asymmetry caused by swash infiltration for gravel beaches however swash infiltration is likely to be the dominant factor in controlling the beachface gradient with increased hydraulic conductivity i e sediment size resulting in steeper beachface gradients c 2001 elsevier science b v all rights reserved

quantitative predictions of beach face slopes application of dimensional analysis to the major factors responsible for beach slope changes yields the dimensionless parameter h b g 0 5 d 0 5 t where h b is the breaking wave height t is the wave period d is the sediment grain size and g is the acceleration due to gravity relationships between this parameter and beach face slope tan are determined by using the existing laboratory and field data to yield tan 0 013 h b g 0 5 d 0 5 t 2 0 15 for the laboratory and tan 0 12 h b g 0 5 d 0 5 t 0 5 for the field these equations make possible the prediction of the beach slope

a note on alongshore sediment transport on weakly curvilinear coasts and its implications abstract this paper presents a simple approximation for assessment of the alongshore sediment transport rate on dissipative weakly curvilinear coasts the approximation considers spatial variations in the wave angle and energy sediment size beach slope and type of wave breaking inside the surf zone similar approaches were employed in the past for coasts forced by high oblique waves where shoreline undulations frequently develop with our approach we can analyze more realistic situations i e alongshore relations between the sediment size and the beach slope the general expression for alongshore sediment transport is made explicit using a simple model for wave propagation the solution is used to examine the implications of the behavior of alongshore sediment transport on shoreline evolution after the analysis of the effects of variations in the wave conditions the alongshore beach slope distribution and the shoreline geometry three different shoreline tendencies were obtained for undulating shorelines migration for changes in deep water wave angle amplitude growth for increases in wave height or period and changes in shoreline geometry and wavelength changes and asymmetries for coasts with alongshore changes in beach slope our results also indicate that wave setup may enhance the formation of undulating shoreline features

interannual variability in the mid and low latitude western north pacific abstract twenty two years 1967 88 of hydrographic data collected by the japan meteorological agency along the 137 e meridian and surface wind data compiled by florida state university fsu were analyzed to study the interannual variability in the western north pacific in the midlatitude region north of 22 n the dominant signal in the dynamic height field was the interannual path variations of the kuroshio whereas the eastward transport of the kuroshio itself had no significant changes between the straight path and meander path years the net transport of the kuroshio system including recirculations showed a 30 increase during the meander path years in the straight path years when the net transport was small the kuroshio tended to take a straight path with a strong recirculation developed to the south the interannual path variations of the kuroshio strongly influenced the water mass movement in the midlatitudes during the kuroshio meander years we found that a significant portion of the north p

contrast of metamorphic and structural histories across the work channel lineament coast plutonic complex british columbia a prominent topographic lineament along the western margin of the coast plutonic complex of southeast alaska and adjacent parts of british columbia separates terranes of contrasting metamorphic histories where it enters british columbia near prince rupert as the work channel lineament the western terrane preserves a regional medium high pressure metamorphic facies series increasing from chlorite grade in the west to kyanite muscovite migmatite near the lineament the metamorphic structural and age relations of the western terrane are consistent with a model of crustal thickening accompanied by westward transport of higher over lower grade metamorphic units during the jurassic this terrane was uplifted and cooled by cretaceous time 85 ma east of work channel lineament high temperature relatively low pressure assemblages are overprinted onto high pressure assemblages the low pressure metamorphic assemblages developed in the eocene during rapid uplift 2 mm yr of rocks which initially may have been metamorphosed at the same time and along the same pt gradient as those of the western terrane structures along the work channel lineament suggest vertical motion during uplift of the eastern terrane and after metamorphism of the western terrane because the metamorphic discontinuity across the lineament is 3 5 kbar at about 700 the lineament in the prince rupert area marks a major crustal break

water table outcropping on macro tidal beaches a simulation model abstract during the fall of the tide the coastal water table within a beach may become decoupled from the ocean resulting in the formation of a seepage face where water outcrops on the inter tidal profile a simulation model called seep is developed to simulate the point of decoupling and the subsequent motion of the seepage face as it continues to fall across the inter tidal profile the model is based entirely on the dynamics of an isolated water particle on the seepage face i e the pressure distribution within the beach is ignored sensitivity analysis of the seep model to beach face slope and permeability characteristics suggests that small variations to these parameters can result in significantly differing rates of exit point motion and hence seepage face extent to test the predictive capability of the seep model results are presented from a field investigation of exit point dynamics on a macro tidal beach north queensland australia the simulation model is found to accurately reproduce the observed seepage face motion at this field site in addition a re analysis of seepage face extent reported in nielsen 1990 from a protected micro tidal environment shows similarly strong agreement between the reported and modelled exit point elevation

on the seasonal eddy variability in the kuroshio extension abstractusing a recently developed tool multiscale window transform mwt and the mwt based canonical energy transfer theory this study investigates the seasonal eddy variability in the kuroshio

changes to monterey bay beaches from the end of the 1982 83 el nino through the 1997 98 el nino abstract the shoreline of monterey bay ca usa demarcates the landward extent of the monterey bay national marine sanctuary along the length of that shoreline nine beaches were profiled 34 times between 1983 and 1998 the resulting data set provides an understanding of processes that affect beach volume width and shape monterey bay which is open to high energy waves generated in the pacific ocean comprises a range of beach environments that respond in a dramatic way to major storms such as the anomalously large el ninos in 1982 83 and 1997 98 this study relates the profile characteristics of the beaches to storminess shoreline location and geomorphic setting because the large el ninos occurred at the start and end of the study the surveys cover both periods of nearly constant beach size and periods of extreme erosion and the data show both the extent of erosion and accretion and the nature of the transition between the two periods

modelling the time varying extent of groundwater seepage on tidal beaches the outcrop of groundwater on tidal beaches distinguishes an upper unsaturated region from a lower saturated region of the intertidal profile since the 1940s it has been recognized that the extent of groundwater seepage at the beach face is one factor determining the tendency for erosive or accretionary conditions to prevail as a primary step towards incorporating bed saturation characteristics within cross shore sediment transport models this paper and accompanying program disk details a simple model to simulate the time varying extent of seepage face development across tidal beaches from a comparison with field results obtained on the macrotidal central queensland australia coast the model appears to provide an encouraging degree of predictive capability the model also assists in highlighting the sensitivity of seepage face development to varying beach face tide and wave characteristics

corrigendum to instability of the north pacific subtropical countercurrent j phys oceanogr 44 2014 818 833 doi 10 1175 jpo d 13 0162 1

why are there upwellings on the northern shelf of taiwan under northeasterly winds upwellings are observed on the northern shelf of taiwan during northeasterly winds analytical and realistic numerical models are used to explain how vertical motions are created by divergence and convergence produced by wind acting on the vorticity field of two strong jets the kuroshio and the taiwan warm current the seaward increase in cyclonic vorticity near the kuroshio s western edge favors a stronger ekman transport away from the jet producing upwelling at the shelfbreak under a northeasterly wind a similar mechanism for generating vertical motions is found across the taiwan warm current the numerical model results indicate that the vorticity effects can account for up to 30 50 of the total variation in the surface ekman transport except during summer s weak southwesterlies northeasterly wind is dominant over the east china sea suggesting that the vorticity effects may be prominent in the observed shelfbreak upwelling in nonsummer months

concurrent decadal mesoscale eddy modulations in the western north pacific subtropical gyre abstractsatellite altimeter data of the past two decades are used to investigate the low frequency mesoscale eddy variability inside the western north pacific subtropical gyre eddy activity modulations with a decadal time scale are detected concurrently within the 18 28 n band including the three branches of the subtropical countercurrent stcc and the hawaiian lee countercurrent hlcc lagging behind the pacific decadal oscillation pdo index by six months enhanced eddy activities were detected in 1995 98 and 2003 06 whereas the eddy activities were below the average in 1999 2002 and 2009 11 analysis of the temperature and salinity data that became available after 2001 via the international argo program reveals that the modulating eddy activities are due to the decadal change in the upper ocean eastward shear in the broad scale stcc hlcc band by conducting an upper ocean temperature budget analysis the authors found that this observed eastward shear change can be effectively accounted for by t

suspended sediment transport mechanisms in high energy swash abstract measurements of suspended sediment concentration at three heights above the bed and cross shore velocity at a single height were obtained using miniature optical backscatter sensors and a miniature electromagnetic current meter from the swash zone of a high energy macrotidal dissipative beach time series from relatively low h s 0 8 m and high h s 2 2 m energy conditions were chosen for analysis possible onshore and offshore sediment transport mechanisms are identified as a sudden offshore to onshore velocity transition and turbulence in the swash front leading to subsequent onshore advection by the uprush and b low frequency high velocity backwashes exceeding a certain threshold for sediment suspension these mechanisms are related to the velocity field through skewness and asymmetry an increase in negative infragravity skewness in high energy conditions suggests a potential shift towards offshore net transport time averaged vertical profiles of cross shore suspended sediment flux were calculated from the velocity and concentration time series these show a tendency towards offshore transport in high energy conditions particularly at low levels in the water column the actual sediment fluxes are believed to be more offshore than those calculated one reason for this discrepancy is the inability of the instruments to detect swash activity at very low levels in the water column

preliminary results central gneiss complex of the coast range batholith southeastern alaska the roots of a high k calc alkaline arc abstract the central gneiss complex cgc of the coast range batholith is the oldest unit of the batholith east of ketchikan alaska being dated by the zircon u pb method by t w stern at 128 140 ma heterogeneous layered commonly migmatitic orthogneiss of hornblende biotite quartz diorite tonalite quartz monzodiorite and granodiorite compositions iugs terminology form the major part of the cgc these gneisses show a range of 50 65 sio2 and are high in al2o3 c 15 19 k2o 1 5 4 and sr 800 900 ppm most major elements show coherent typically magmatic trends with sio2 la and rb show maxima at 58 sio2 initial 87sr 86sr ratios are relatively high and range from 0 7052 to 0 7066 wallrocks of the cgc are mostly metagraywacke pelite and metavolcanic rocks at amphibolite facies they are geochemically dissimilar to the cgc major and minor elements of the cgc are very similar to those of high k orogenic calc alkaline andesitic suites the cgc may have formed largely by fractionation of mantle derived high al k sr basaltic liquid in an ascending diapir having hornblende plagioclase and biotite as major precipitating phases the cgc probably represents the plutonic equivalent of a continental margin or andean arc that formed when the taku terrane of the insular belt on the west collided with the previously emplaced but also allochthonous stikine terrane on the east in late jurassic or early cretaceous time

from fine sand to boulders examining the relationship between beach face slope and sediment size abstract it is a long standing maxim that coarser sediment sizes are associated with steeper beach face slopes but because most work has focused on sandy beaches few data are available for the pebble cobble or boulder size ranges little is known therefore about how beach morphology and grain size relate at the coarser size grades we compiled data from the literature 2144 measurements of beach face slope with associated grain sizes covering the range from very fine sand to boulders this meta analysis shows that beach faces do tend to steepen as average grain size increases at least up to the cobble size range but the trend is not simple although previous studies suggested a simple power law relationship between grain size and beach face slope in fact the data distribution is best fit by a curve that is steep at the finer grain sizes but is much more gentle as grain size coarsens and may trend downward for boulders fine and medium sands have the greatest range of reported slopes and the data support the importance of effective weight modification and boundary layer dynamics as primary controls on beach face steepness at these fine size grades around the very coarse sand size grade a plateau marks a shift in beach dynamics as hydraulic conductivity increases beaches switch to being infiltration dominated the trend toward steeper slopes continues but at a lower and steady rate from granules through cobbles there appears to be a falloff in slope for the coarsest boulder deposits but we note that this is based on very few locations so should be considered preliminary the overall data distribution is described by a power law function tan a d 50 0 125 b c the broadness of each transition zone also shows that a range of factors other than grain size governs where that tipping point occurs in the cobble and boulder size ranges there are two deposit categories boulder beaches and supratidal boulder ridges although not commonly thought of as beaches boulder ridges record long term storm deposition and reworking on the highest energy coasts supratidal ridges and boulder beaches seem to show different slope grain size relationships with the steepest slopes occurring in boulder ridges and with boulder beaches showing more gentle gradients than other coarse clastic beaches but our data set reveals how little quantitative information exists about the coarsest end of the beach spectrum and invites further work to investigate the sedimentology of cobble and boulder dominated systems

land falling typhoons are controlled by the meridional oscillation of the kuroshio extension low frequency variations of typhoon paths are often attributed to changes in the north pacific subtropical high and monsoon through influences on the steering wind evidence indicates however a strong imprint of the kuroshio on the atmosphere here we show that the meridional oscillation of sea surface temperature sst front over the kuroshio extension east of japan significantly correlates with the number of land falling typhoons along east asia from june to october accounting for 70 of the low frequency variance since 1980 we used observations and a simple model to show that when the sst front shifts poleward equatorward sst gradient south of the current and westerly tropospheric wind weaken strengthen steering more typhoons to veer toward away from the east asian continent our analysis also indicates that long term weakening of sst gradient and westerly wind appears to be concomitant with poleward shifting of the kuroshio attributed to global warming in some studies and suggests the potential for more land falling typhoons in east asia in the coming decades

magma mixing in granitic rocks of the central sierra nevada california abstract the el capitan alaskite exposed in the north american wall yosemite national park was intruded by two sets of mafic dikes that interacted thermally and chemically with the host alaskite comparisons of petrographic and compositional data for these dikes and alaskite with published data for sierra nevada plutons lead us to suggest that mafic magmas were important in the generation of the sierra nevada batholith specifically we conclude that 1 intrusion of mafic magmas in the lower crust caused partial melting and generation of alaskite rhyolitic magmas 2 interaction between the mafic and felsic magmas lead to the observed linear variation diagrams for major elements 3 most mafic inclusions in sierra nevada plutons represent chilled pillows of mafic magmas related by fractional crystallization and granitoid assimilation that dissolve into their felsic host and contaminate it to intermediate granodioritic compositions 4 vesiculation of hydrous mafic magma upon chilling may allow buoyant mafic inclusions and their disaggregation products to collect beneath a pluton s domed ceiling causing the zoning mafic margins to felsic core that these plutons exhibit

u pb geochronology of late cretaceous and early tertiary plutons in the northern coast mountains batholith u pb geochronologic studies demonstrate that steeply dipping sheetlike tonalitic plutons along the western margin of the northern coast mountains batholith were emplaced between 83 and 57 perhaps 55 ma less elongate tonalitic granodioritic bodies in central portions of the batholith yield ages of 59 58 ma coeval with younger phases of the tonalitic sheets large granite granodiorite bodies in central and eastern portions of the batholith were emplaced at 51 48 ma trends in ages suggest that the tonalitic bodies generally become younger southeastward and that at the latitude of juneau plutonism migrated northeastward across the batholith at 0 9 km ma variations in the age shape location and degree of fabric development among the various plutons indicate that late cretaceous paleocene tonalitic bodies were emplaced into a steeply dipping dip slip shear zone that was active along the western margin of the batholith postkinematic eocene plutons were emplaced at shallow crustal levels inhe

effects of the stcc eddies on the kuroshio based on the 20 year jcope2 reanalysis results abstract in this study 20 years of model reanalysis data are analyzed to study the effects of the subtropical countercurrent stcc eddies on the upstream kuroshio from east of luzon to east of taiwan the effects are assessed from individual events to interannual time scales the wind driven kuroshio is modified by the stcc eddies with high spatiotemporal variations the mass balance in the composite eddy events indicates that the strengthening and weakening of the kuroshio transport are locally caused by the mass convergence and divergence produced by the eddies the same analogy applies to the interannual time scale in the eddy rich years the upstream kuroshio is generally stronger because of wind forcing yet the strengthening is nonuniform because of modification by the eddies the larger number of warm eddies to the east of taiwan and luzon island further strengthen the jet whereas the larger number of cold eddies to the east of the luzon strait weaken the kuroshio in the luzon strait drifter trajectories show larger luzon strait intrusion during the occurrence of cold eddies the local weakening of the kuroshio by cold eddies leads to a weaker potential vorticity jump producing favorable conditions for the intrusion of a water mass into the south china sea

mixed layer instabilities and restratification abstract the restratification of the oceanic surface mixed layer that results from lateral gradients in the surface density field is studied the lateral gradients are shown to be unstable to ageostrophic baroclinic instabilities and slump from the horizontal to the vertical these instabilities which are referred to as mixed layer instabilities mlis differ from instabilities in the ocean interior because of the weak surface stratification spatial scales are o 1 10 km and growth time scales are on the order of a day linear stability analysis and fully nonlinear simulations are used to study mlis and their impact on mixed layer restratification the main result is that mlis are a leading order process in the ml heat budget acting to constantly restratify the surface ocean climate and regional ocean models do not resolve the scales associated with mlis and are likely to underestimate the rate of ml restratification and consequently suffer from a bias in sea surface temperatures and ml depths in a

wave set up on a natural beach wave set up the superelevation of mean water level owing to the presence of breaking incident waves was measured at the shoreline of a natural beach offshore pressure sensors monitored incident wave conditions the set up of the shoreline was found to be about 0 17hs where hs is the significant wave height in deep water

eocene 51 ma end to northward translation of the coast plutonic complex paleomagnetism and k ar dating of the white pass dikes abstract the white pass mafic dikes are located in the coast belt inboard of the coast shear zone denali fault system east of skagway alaska astride the alaska british columbia border the dikes intrude eocene felsic plutons in the coast plutonic complex three k ar analyses date the dikes at 51 9 0 8 ma biotite 50 1 1 0 ma and 45 0 0 8 ma both whole rock structural analysis on these vertical dikes indicates that the study area has not been tilted significantly since dike emplacement conventional alternating field and thermal step demagnetization and saturation remanence paleomagnetic methods were used to analyse 407 specimens from 27 dike and five host rock sites three contact tests show that the specimens retain a primary thermoremanent magnetization trm carried in pseudosingle to multidomain magnetite although some magnetization in a few dikes is carried by pyrrhotite the dual polarity trm is mostly reversed and the 24 accepted dike sites give a pole position of 245 7 e 76 3 n dp 4 2 dm 4 4 indicating a paleolatitude discordance of 8 4 south and a clockwise rotation of 40 9 with respect to the north american craton these data along with other paleomagnetic data on eocene rocks indicate that the allochthonous eastern coast and intermontane belt terranes had halted their northward translation by about 51 ma but continued to be rotated clockwise by an average of 24 10 thereafter probably on underlying sole faults

geodynamic evolution of the southern abitibi and pontiac terranes evidence from geochemistry of granitoid magma series 2700 2630 ma four distinct granitic series developed during the evolution of the archean abitibi southern volcanic zone svz 1 a minor synvolcanic tonalite trondhjemite granodiorite ttg series was emplaced at 2700 ma which has extremely low k2o 1 5 wt rb 50 ppm and sr 200 ppm higher nb y and sc flat rare earth element ree patterns and negative eu anomalies 2 a voluminous tonalite granodiorite granite quartz monzonite tggm series developed syntectonically at 2695 2685 ma and displays low k2o 1 3 wt rb 10 50 ppm ba 1000 ppm and u enhanced sr depletion of ta nb and ti and strongly fractionated ree patterns la ybn 49 21 3 a late tectonic quartz syenite quartz monzonite granite smg series was emplaced from 2685 to 2675 ma and is grossly similar to the tggm but has lower cao k2o na2o and greater concentrations of rb ba th and u 4 a late tectonic to posttectonic alkali feldspar syenite alkali feldspar quartz syenite ss series was emplaced

structural and geochronologic relations along the western flank of the coast mountains batholith stikine river to cape fanshaw central southeastern alaska abstract geologic and u pb geochronologic studies in central southeastern alaska provide constraints on the mid cretaceous to mid tertiary deformation west of the coast mountains batholith the ne dipping sumdum and fanshaw faults record the w directed emplacement of the ruth assemblage yukon tanana terrane and taku terrane over the subjacent gravina belt and alexander terrane ductile fabrics of the sumdum fanshaw fault system truncate early formed foliation and thrust faults in albian and older gravina belt strata u pb age data from syn and post tectonic plutons suggest that deformation was ongoing at 92 9 3 0 ma but had mostly ceased by 90 ma the sumdum fanshaw fault system marks the tectonic boundary between the alexander wrangellia terrane and inboard yukon tanana and stikine terranes and lies within a thrust belt that extends from southern alaska to northern washington mid cretaceous structures are truncated to the east by ne dipping ductile fabrics of the coast shear zone sheet like paleocene tonalites were emplaced into and deformed within the shear zone undeformed mid eocene dikes cross cut the tonalites kinematic relations in the coast shear zone suggest a complex displacement history that includes both east side up reverse and west side up normal shear the shear zone probably accommodated the collapse of overthickened crust developed during mid cretaceous shortening

decadal variability of the subtropical front of the western north pacific in an eddy resolving ocean general circulation model 1 we examined decadal variability of the subtropical front stf of the western north pacific by using a north pacific ocean general circulation model ogcm comparing the results of three simulations with different horizontal resolutions in the long term mean fields the eddy resolving model 10 km was able to simulate the distributions of the stf and the associated subtropical countercurrent stcc between 20 n and 30 n better than either the non eddy resolving model 100 km or the eddy permitting model 20 km because it simulated the kuroshio recirculation gyre more realistically the simulated stf intensity exhibited significant decadal scale variations it was stronger in the late 1970s and weaker in the early 1990s during these two periods the simulated mode waters showed corresponding differences in their potential vorticity minima density and paths we also investigated the relationship between the decadal scale stf variability and atmospheric forcing the results suggest that the decadal scale stf variability can be largely explained by changes in the mode waters formed in the western north pacific and advected to north of the stf by the subtropical gyre in response to a change in surface westerly winds that occurred in the mid 1970s

rapid dewatering of the crust deduced from ages of mesothermal gold deposits the large scale migration of fluids through the continental crust has been well documented but there is no consensus regarding the timing of fluid migration relative to orogenic episodes or rates of crustal dewatering1 here we present40ar 39ar dates for muscovites from quartz veins along a major shear zone in southeast alaska which show that the veins were emplaced in the early eocene during the late stages of orogenic deformation hydrother mal activity took place for only about 1 myr and along a distance of at least 200 km the fluids were generated by metamorphic reactions in subducted crust along the north american plate margin and were apparently trapped in the crust by the low permeabilities accompanying a convergent tectonic regime until 56 myr ago the rapid dewatering event coincided with a change in plate motion at 56 55 myr which caused a shift from convergent to partly transcurrent tectonics we suggest that this change in tectonic regime led to increased crustal permeabilities and hence the possibility of large scale fluid migration

new u pb age constraints on latest cretaceous magmatism and associated mineralization in the fawnie range nechako plateau central british columbia new u pb ages and k ar dates primarily for rocks proximal to mineral occurrences in the fawnie range of central british columbia document latest cretaceous ca 74 66 ma continental arc igneous activity and date associated base and precious metal mineralization u pb ages of ca 73 69 ma for the capoose pluton and hypabyssal to extrusive garnet rhyolites at the capoose prospect demonstrate a latest cretaceous age for mineralization and a likely plutonic source for mineralizing fluids a u pb age of ca 67 ma for a late mineralized felsic dyke and two k ar dates ca 70 and 68 ma for hornfelsed jurassic volcanic rocks at the blackwater davidson prospect constrain a latest cretaceous age for mineralization a u pb age of ca 74 ma for a fine grained diorite sill that cuts a significant epithermal gold vein at the tsacha prospect places a minimum age on mineralization at this probable jura cretaceous deposit and documents latest cretaceous magmatism latest cretaceous k ar dates are reported for an andes

grain size and depositional environment as predictors of permeability in coastal marine sands more than half of the surface sediments covering the continental shelves are sandy which may permit substantial sub seafloor pore water advection knowledge of sediment permeability is required for quantifying advection and associated solute transport but studies of marine sediments typically report grain size analyses rather than permeability here data from 23 studies were examined to determine the range in permeabilities reported for sublittoral marine sands and to assess the utility of permeability grain size relationships in this setting in the resulting database the permeability of small w30 cm undisturbed cores collected from the sea floor all fell between 2 10 12 and 4 10 10 m 2 a range where advective transport induced by wave and current action should be pervasive the range in grain size was very similar for near shore 10 m water depth but the permeability of the continental shelf samples was consistently lower for the same median grain size empirical permeability grain size relationships generated a poor fit r 2 0 35 for the aggregate data but separate relationships for near shore and continental shelf samples were significantly better r 2 0 66 and 0 77 respectively permeability grain size relationships thus may be useful for sublittoral sands but a larger database needs to be accumulated before reliable fit parameters and variability can be predicted thus it is recommended that permeability be routinely determined when characterizing sedimentological properties of marine sand deposits concurrent determinations of sediment bulk density and porosity may further improve estimates of permeability 2008 published by elsevier ltd

onshore offshore sediment transport on beaches abstract the onshore offshore transport of sediment on beaches in analyzed by considering the time averaged behaviour of a control volume bounded by the wave breaking zone and by the beach face interactions are determined between the wave radiation stress the wave set up the shear stress on the beach face and the beach permeability simple theoretical relationships are derived which specify beach slope in terms of incident wave attack and beach material properties these relationships indicate that coarser sediment beaches are steeper because of the higher beach permeability it is also shown that any particular beach will decrease its slope as the wave attack increases according to an inverse function of the wave height not only the beach permeability but also the sediment grading curve is shown to be a key factor in determining beach slope the theory is used to discuss and explain some observed behaviour on real beaches and the possible implications for beach failure under storm attack

a northern cordilleran ocean continent transect sitka sound alaska to atlin lake british columbia the 155 km wide 310 km long sitka sound atlin lake continent ocean transect includes almost all the geologic geophysical and geotectonic elements of the canadian cordillera it crosses the chugach wrangellia alexander stikine and cache creek terranes the gravina and laberge overlap assemblages intrusive and metamorphic belts and neotectonic faults that bound major blocks linear belts of magnetic highs are associated with jurassic and cretaceous granitic belts in wrangellia and the western and central parts of the alexander terrane and with the granitic rocks of the coast plutonic metamorphic complex cpmc the border ranges fault may be expressed at depth on either side of the peril strait fault an enigmatic northeast trending gradient in the cpmc and adjacent rocks separates a regional magnetic low to the northwest from a 300 nt high field to the southeast the bouguer gravity field decreases in broad steps from pacific crust high values to lows at the international boundary with pronounc

dehydration melting of a basaltic composition amphibolite at 1 5 and 2 0 gpa implications for the origin of adakites this study presents the results of dehydration melting experiments on a basaltic composition amphibolite under conditions appropriate to a hot slab geotherm 1 5 and 2 0 gpa and temperatures of 850 to 1150 c dehydration melting produces an omphacitic augite and garnet bearing residue coexisting with rhyolitic to andesitic composition melts at 1 5 gpa the amphibolite melts in two stages between 800 and 1025 c the 2 0 gpa data also define two melting stages at 2 0 gpa the first stage involves nearly modal melting of the original amphibolite minerals qtz pl amp to produce melt cpx grt during the second stage the eclogite restite melts non modally 0 86 cpx 0 14 grt 1 melt the experimental results were combined with data from the literature to generate a composite p t phase diagram for basaltic composition amphibolites over the 800 to 1100 c temperature range for pressures up to 2 0 gpa comparison of the major element compositions of the experimentally produced melts with compositions of presumed slab melts adakites shows that partial melting of amphibolite at conditions appropriate to a hot slab geotherm produces melts similar to andesitic and dacitic adakites except for significant mgo and cao depletions trace element modelling of amphibolite dehydration melting using the 2 0 gpa melting reactions produces ree abundances similar to those of adakites at 10 15 wt batch melting but the models do not reproduce the high sr y ratios characteristic of adakites taken together the major and trace element results are not consistent with the derivation of adakites by dehydration melting of the subducted slab with little or no interaction with the mantle wedge or crust if adakites are partial melts of the subducted slab they must undergo significant interaction with the mantle and or crust during which they acquire a number of their distinctive characteristics

provenance of holocene beach sand in the western iberian margin the use of the kolmogorov smirnov test for the deciphering of sediment recycling in a modern coastal system

instability of the north pacific subtropical countercurrent abstractthe north pacific subtropical countercurrent stcc has a weak eastward velocity near the surface but the region is populated with eddies studies have shown that the stcc is baroclinically unstable with a peak growth rate of 0 015 day 1 in march and the 60 day growth time has been used to explain the peak eddy kinetic energy eke in may observed from satellites it is argued here that this growth time from previously published normal mode instability analyses is too slow growth rates calculated from an initial value problem without the normal mode assumption are found to be 1 5 to 2 times faster and at shorter wavelengths due to the existence of i nonmodal solutions and ii sea surface temperature front in the mixed layer in winter at interannual time scales it is shown that because of rapid surface adjustments the stcc geostrophic shear hence also the instability growth is approximately in phase with surface forcing leading to eke modulation that peaks approximately 10 months later

one year along beach variation in the maximum depth of erosion resulting from irregular shoreline morphology abstract beach erosion and accretion occur across multiple time scales over long time scales decades to millennia the shoreface ravinement surface which is recognized as a coarse lag deposit forms at the shoreface toe as a result of wave and current induced erosion during shoreline transgression over short time scales hours to days the depth of sediment disturbance which is recognized as coarse lamina and measured at the foreshore by devices and monitoring tracer beds forms as a result of wave and current induced reworking during a tidal cycle the maximum depth of erosion mdoe quantified here over 1 year is modulated by processes that operate over a time scale that is between the drivers of short term e g tides and waves and long term e g sea level rise beach erosion the mdoe integrates the erosion that occurs over a discrete time interval and records the maximum depth of erosion that is likely principally induced by storms which is difficult to quantify by other methods that rely on discrete observations e g changes in elevation or movement of the mean high water line a novel technique for quantifying the mdoe based on comparing the bedding and stratigraphy between cores collected at the same locations over a discrete time interval is presented here and applied at onslow beach nc usa this 12 km long barrier island has irregular shoreline morphology characterized by two embayments separated by a central headland this shape is largely the result of variations in the depth of underlying rock strata and produces a steeper beachface at the headland than at the embayments at each of the six sites examined along the barrier the mdoe is found to increase from the backshore to the middle intertidal zone and is higher at the sites closer to the headland these variations in the mdoe are likely due to the increase in average wave energy impacting the beachface from an offshore direction and steeper beaches intermediate beach state at the headland where the mdoe is within the beach facies it is not associated with a coarsening which is due to the heterolithic nature of the onslow beach strata where the mdoe is the contact between back barrier and beach facies it is always associated with a coarsening and a gravel rich lag deposit because in this case the mdoe is an amalgamation of multiple erosional events which is similar to the shoreface ravinement surface along beach variation in the mdoe does not correspond with discrete observations of beach change over the same period and is likely a better indicator of erosion potential than long term discrete observations such as changes in surface elevation or the position of the mean high water line

vortices of the mediterranean sea an altimetric perspective the presence of coherent vortices makes observed mesoscale fields of the ocean resemble twodimensional turbulence using this analogy a common definition of a coherent structure has been used to study the statistical properties of mediterranean sea vortices observed by satellite altimeters over a 7 yr period a vortex has been defined as the simply connected region with values of the okubo weiss parameter w 0 2w where w is the spatial standard deviation of w and the same sign of vorticity this definition is shown to be appropriate to detect and characterize statistically properties such as size mean kinetic energy and amplitude of vortices in the mediterranean basin from sea level anomaly maps corresponding to the period from october 1992 to october 1999 the distribution of such properties for the mediterranean vortices suggests a heuristic criterion to extract and select very coherent and long lived vortices from the whole set of structures identified in altimetric maps such coherent vortices appear to be selected for amplitudes greater than 2w where the amplitude has been defined in terms of the okubo weiss parameter rather than vorticity and strongly correspond to those reported from observations with independent data systematic locating and tracking of such vortices provide for the first time a general picture of their preferential paths in the mediterranean basin which are characterized by complex but rather well defined patterns

flow velocity and sediment transport in the swash zone of a steep beach detailed measurements of flow velocity and total sediment load were obtained in the swash zone on a steep beach swash motion was measured using ducted impeller flow meters and capacitance water level probes during wave uprush the onshore flow increased almost instantaneously from zero to its maximum velocity after the arrival of the leading edge of the swash lens and subsequently decreased gradually to zero for the remainder of the uprush during backwash the offshore flow increased steadily from zero to its maximum towards the end of the backwash and dropped rapidly to zero as the beach fell dry the duration of backwash was typically longer than that of uprush and maximum water depth on the beach was attained just prior to the end of the uprush the total sediment load was measured for 35 individual wave uprush events using a sediment trap the amount of sediment transported by a single uprush was typically two to three orders of magnitude greater than the net transport per swash cycle difference between uprush and backwash inferred from surveys of beach profile change the measured immersed weight total load transport rate displayed a strong relationship with the time averaged velocity cubed which is consistent with equations for both bedload transport and total load transport under sheet flow conditions the bagnold 1963 1966 bedload transport model was tested against our field data and yielded ib ku3tu tan tan where ib is the immersed weight of bedload transported during the entire uprush kg m 1 k is a coefficient kg m 4 s2 u is the time averaged flow velocity for the uprush m s 1 tu is the uprush duration s is the friction angle of the sediment and is the beach slope the empirically determined value for the coefficient k was 1 37 0 17

interannual variability of the north pacific subtropical countercurrent and its associated mesoscale eddy field interannual changes in the mesoscale eddy field along the subtropical countercurrent stcc band of 188 258n in the western north pacific ocean are investigated with 16 yr of satellite altimeter data enhanced eddy activities were observed in 1996 98 and 2003 08 whereas the eddy activities were below average in 1993 95 and 1999 2002 analysis of repeat hydrographic data along 1378e reveals that the vertical shear between the surface eastward flowing stcc and the subsurface westward flowing north equatorial current nec was larger in the eddy rich years than in the eddy weak years by adopting a 2 layer reduced gravity model it is shown that the increased eddy kinetic energy level in 1996 98 and 2003 08 is because of enhanced baroclinic instability resulting from the larger vertical shear in the stcc nec s background flow the cause for the stcc nec s interannually varying vertical shear can be sought in the forcing by surface ekman

eddy transport of heat and thermocline waters in the north pacific a key to interannual decadal climate variability abstract high resolution xbt transects in the north pacific ocean at an average latitude of 22 n are analyzed together with topex poseidon altimetric data to determine the structure and transport characteristics of the mesoscale eddy field based on anomalies in dynamic height 410 eddies are identified in 30 transects from 1991 to 1999 including eddies seen in multiple transects over a year or longer their wavelength is typically 500 km with peak to trough temperature difference of 2 2 c in the center of the thermocline the features slant westward with decreasing depth by 0 8 of longitude on average from 400 m up to the sea surface this tilt produces a depth varying velocity temperature correlation and hence a vertical meridional overturning circulation in the mean 3 9 sv sv 106 m3 s 1 of thermocline waters are carried southward by the eddy field over the width of the basin balanced mainly by northward flow in the surface layer corresponding northward heat transport is 0 086 0 012 pw

swash infiltration exfiltration and sediment transport field measurements of vertical pore pressure gradients within the bed are used to quantify instantaneous 8 hz rates of swash infiltration exfiltration across the beach face cyclic infiltration exfiltration is associated with individual swash events with observed vertical flow rates o 10 3 m s rates of net swash groundwater exchange i e through bed flow integrated over several swash cycles are two orders of magnitude smaller at the timescale of individual swashes vertical pore pressure gradients within the beach face are much greater than horizontal pore pressure gradients this permits application of the numerical solution of darcy s law for one dimensional vertical flow to model fluctuating pore pressures and hence vertical through bed flow vertical flow through a porous bed modifies sediment mobility in at least two ways 1 seepage forces change the effective weight of surficial sediments and 2 boundary layer thickening or thinning result in altered bed shear stresses by considering these two opposing effects separately a new shields parameter is derived that incorporates terms for through bed flow simulation of time varying seepage force and bed stress effects over an uprush backwash cycle suggests that the effect of altered bed stresses dominates over the change in effective weight and that infiltration exfiltration effects are most important during uprush simulated transport rates are increased by up to 40 of the peak transport rate during uprush and reduced by 10 during backrush in summary swash infiltration exfiltration across a saturated beach face enhances the net upslope transport of sediment

physical modelling of tsunami onshore propagation peak pressures and shielding effects in an urban building array abstract wave experiments were conducted on a 1 20 length scale to measure water surface elevations and extreme pressures on and around idealized structural elements and arrays of structures experiments varied offshore wave characteristics and onshore structural configurations conditions in which waves broke on or just before the specimen caused maximum impulsive pressures pressures measured under nonbreaking wave conditions agreed with predicted values using design equations suggested by the japanese cabinet office however bare earth water surface elevation inputs produced nonconservative estimates in breaking wave trials shielded structures experienced pressure reductions of 40 70 under breaking wave conditions results indicate that shielding elements constructed nearshore may reduce wave induced damage this dataset may be used to validate numerical models of tsunami propagation through urban environments

swash zone sediment suspension and transport and the importance of bore generated turbulence a study of swash zone sediment transport was conducted at gleneden beach oregon during february 25 28 1994 the data collected included suspended sediment concentration ssc sea surface elevation and velocity initially 4 and 8 cm above the bed at three cross shore locations within the swash zone spanning high tides ensemble averages of 6 9 and 12 s duration swash events showed that the uprush suspension was high concentrated in the leading edge and nearly vertically uniform above the lower 1 2 cm of the water column shortly after the sensors were inundated by run up the sediment rapidly settled out of the water during flow reversal the ssc was small but increased again in the backwash backwash vertical profiles were markedly different from uprush profiles with much of the suspension being confined to very near the bed where strong vertical gradients in ssc existed these marked differences show that the backwash is not simply the reverse of the uprush implying significant differences in the underlying fluid dynamics and sediment transport mechanisms backwash sediment suspension increased with flow duration however ensemble averaged ssc profiles of varying duration showed that the backwash concentrations were not consistent at the same temporal phases which suggests that water depth in addition to flow duration may be a controlling factor strong cross shore gradients in ssc suggest that bore derived turbulence may affect local sediment transport specifically our data show this bore generated turbulence turbulent kinetic energy directly influences local sediment suspension hence standard bed shear bagnold type sediment transport models may no longer be valid in the vicinity of the bore in the vicinity of the bore a higher correlation between bore generated turbulence and suspended sediment transport was found than between a bagnold type formulation and suspended sediment transport

regional scale impact of tidal forcing on groundwater flow in unconfined coastal aquifers summary this paper considers the impact of tidal forcing on regional groundwater flow in an unconfined coastal aquifer numerical models are used to quantify this impact for a wide range of hydrogeological conditions both a shallow and a deep aquifer are investigated with regard to three dimensionless parameter groups that determine the groundwater flow to a large extent analytical expressions are presented that allow for a quick estimate of the regional scale effect of tidal forcing under the same conditions as used in the numerical models quantitatively the results in this paper are complementary to previous studies by taking into account variable density groundwater flow dispersive salt transport and a seepage face in the intertidal area qualitatively the results are in line with previous investigations the time averaged hydraulic head at the high tide mark increases upon a decrease of each of the three considered dimensionless parameter groups r including the ratio of the hydraulic conductivity and the precipitation excess a the slope of the intertidal area and al the ratio of the width of the fresh water lens and the tidal amplitude the relative change of the location and the hydraulic head of the groundwater divide which together characterize regional groundwater flow increase as a and al decrease but decrease as r decreases the difference between the analytical solutions and numerical results is small therefore the presented analytical solutions can be used to estimate the bias that is introduced in a numerical model if tidal forcing is neglected the results should be used with caution in case of significant wave forcing as this was not considered

migmatite structures in the central gneiss complex boca de quadra alaska migmatite structures in the coast plutonic metamorphic complex are well exposed in the inlet of boca de quadra southeast alaska two types of anatectic migmatites are present patch migmatites formed by in situ melting and subsequent crystallization of melt diktyonitic migmatites comprise a discontinuous veined network of leucocratic material in which leucosomes enclose boudins of host rock the margins of these boudins show the development of both melanosomes and shear band fabrics strain analysis of diktyonitic melanosomes indicates that these regions have undergone volume decreases of 20 27 this volume decrease is attributed to melt extraction into the adjacent fracture filling leucosomes thus diktyonitic migmatites formed by shear induced segregation of partial melt whereas in patch migmatites the lack of shear stresses inhibited melt segregation the variable structural style of anatectic migmatites in boca de quadra is not related to host rock composition but may be due to differences in the amount of differential stress during migmatization these in turn may be controlled by host rock strength and or diachroneity of migmatization and deformation determination of volume changes during migmatization using strain analysis is potentially capable of discriminating intrusive and anatectic migmatites and consequently of documenting melt segregation and subsequent migration across crustal levels

short term changes in the morphodynamic states of beaches and surf zones an empirical predictive model a time series of 6 5 years of daily observations of beach states and wave characteristics from southeastern australia was analyzed with the aim of determining the degree to which time varying beach state can be explained and predicted the six commonly occurring beach states dissipative longshore bar trough rhythmic bar and beach transverse bar and rip low tide terrace and reflective discussed earlier were related by means of discrete discriminant analyses to the parameter hb wst where hb is breaker height ws is the fall velocity of the beach sand and t is peak breaker period using a total of 1545 cases two values were used in the analyses the immediate value occurring on the day the particular state was observed and a weighted mean value expressing recently antecedent conditions the immediate value made a negligible contribution to explaining day to day beach state observations however the antecedent conditions showed a strong relationship and provide a successful means of prediction by examining cases where the time derivatives of both state and were near zero it was possible to define the equilibrium conditions associated with each state directions of change erosional or accretionary are predicted in terms of departures of from the equilibrium value appropriate to the beach state prevailing at the time change begins