microbe clay mineral interactions clays and clay minerals are common components in soils sediments and sedimentary rocks and they play an important role in many environmental processes iron is ubiquitous in clays and clay minerals and its oxidation state in part controls the physical and chemical properties of these fine grained minerals the structural ferric iron in clay minerals can be reduced either chemically or biologically biological reductants include mesophilic and thermophilic microorganisms from diverse environments such as soils sediments sedimentary rocks and hydrothermal hot springs multiple clay minerals have been used for microbial reduction studies including dioctahedral smectiteillite series palygorskite chlorite and their various mixtures in natural soils and sediments all of these clay minerals are reducible by microorganisms under various conditions with smectite nontronite being the most reducible and illite the least the rate and extent of bioreduction depends on many experimental factors such as the type of microorganisms and clay minerals solution chemistry and temperature despite significant efforts current understanding of the mechanisms of microbial reduction of ferric iron in clay minerals is still limited whereas some studies have presented evidence for a solid state reduction mechanism others argue that the clay mineral structure partially dissolves when the extent of reduction is high this inconsistency may be related to several experimental conditions and their specific effects are discussed in this paper whereas past experiments have been largely conducted in well controlled laboratory systems recent efforts have attempted to transfer knowledge to the field to improve our understanding of more complex soil systems for better agricultural practices biologically reduced clay minerals are also important agents in remediating inorganic and organic contaminants in soil and groundwater systems this paper reviews the most recent developments and suggests some directions for future research

u and th series disequilibria in coastal infill sediments from praia da rocha algarve region portugal a contribution to the study of late quaternary weathering and erosion u and th series disequilibria observed in a sequence of infill sediments from praia da rocha southern portugal were used in combination with geochemical and particle size data to investigate sediment provenance with a view to resolving the late quaternary weathering and erosion history of the algarve region and the stratigraphy of coastal karstic exposures of the faro quarteira fq formation the red infill units can be distinguished from the brown and buff units on the basis of their lower residual u and th concentrations their differing post depositional histories as revealed by u and th series disequilibria in sequentially extracted sediment phases and their greater degree of sediment processing hence the buff and brown infill units appear to be derived locally from weathering of the miocene limestone whilst the red infill may be linked to large scale mass movement of the fq formation from further inland but south of silves during the late pleistocene this sequence of events confirms a close association between the formation of karst topography and infilling by gravitational slumping debris flow and fluvial activity and hence accounts for the complex three stage sediment provenance of the infill material

bioprotection explored the story of a little known earth surface process abstract bioprotection is identified as an earth surface process however it has been little studied little acknowledged and yet may have major implications for the operation and management of geomorphic systems key early observations are traced back to darwin s voyage of the beagle geikie in the natural environment and watson for the built environment recent field observations and experimental work examining bioprotection are reviewed with a specific focus on lichens and the landscape as are its complex interactions with other processes a conceptual model of bioprotection is presented for the case of an epilithic lichen on a limestone surface

gravitational symmetric and baroclinic instability of the ocean mixed layer abstract a hierarchy of hydrodynamical instabilities controlling the transfer of buoyancy through the oceanic mixed layer is reviewed if a resting ocean of horizontally uniform stratification is subject to spatially uniform buoyancy loss at the sea surface then gravitational instability ensues in which buoyancy is drawn from depth by upright convection but if spatial inhomogeneities in the ambient stratification or the forcing are present as always exist in nature then horizontal density gradients will be induced and within a rotation period horizontal currents in thermal wind balance with those gradients will be set up within the mixed layer there are two important consequences on the convective process upright convection will become modified by the presence of the thermal wind shear fluid parcels are exchanged not along vertical paths but rather along slanting paths in symmetric instability theoretical considerations suggest that this slantwise convection sets the potential vorticity of th

mapping ocean observations in a dynamical framework a 2004 06 ocean atlas abstract this paper exploits a new observational atlas for the near global ocean for the best observed 3 yr period from december 2003 through november 2006 the atlas consists of mapped observations and derived quantities together they form a full representation of the ocean state and its seasonal cycle the mapped observations are primarily altimeter data satellite sst and argo profiles gcm interpolation is used to synthesize these datasets and the resulting atlas is a fairly close fit to each one of them for observed quantities especially the atlas is a practical means to evaluate free running gcm simulations and to put field experiments into a broader context the atlas derived quantities include the middepth dynamic topography as well as ocean fluxes of heat and salt freshwater the atlas is publicly available online www ecco group org this paper provides insight into two oceanographic problems that are the subject of vigorous ongoing research first regarding ocean circulation estimates

coastal landscape evolution as a function of eustasy and surface uplift rate cascadia margin southern oregon we explore the relative importance of eustatic versus tectonic factors in sculpting preserving and modifying coastal landforms the study area is a 30 km coastal reach in southern oregon using degree of soil development as a means of correlating wave cut platforms along the coast we document that surface uplift rate is variable in a shore parallel sense variability being a function of differential vertical displacement of crustal blocks along faults and flexures in the upper plate of the cascadia subduction zone a consequence of this variability is that in areas of moderate uplift rate 0 7 0 9 m k y flights of up to seven emergent wave cut platforms are preserved along the interfluves of coastal drainages whereas in areas of low uplift rate 0 05 0 2 m k y only one wave cut platform commonly exists within a few meters of present sea level preservation of shore platforms in both areas is the result of the inter action of tectonic uplift and eustatic sea level changes operating on a high energy coast subject to platform planation platform reoccupation can be a consequence of late pleistocene eustatic sea level changes operating on low up lift rate coasts particularly in the cases of the 200 ka and 125 ka high sea stands reoccupation by the later highstand is probable when coastal uplift rates are about 0 2 m k y the same eustatic history operating on a higher uplift rate section of the coast results in multiple emergent platforms and no instances of reoccupation coastal drainage basins in the size range of 5 10 km2 have different hypsometries reflecting whether platforms in coastal basins are preserved over a range of altitudes or only near sea level the hypsometric differences are thus a product of differences in uplift rate the dominant mechanism of base level fall varies between the two areas coastal retreat during sea level highstands drives baselevel fall in lower uplift rate basins whereas tectonic uplift mainly drives base level fall in moderate uplift rate basins even though the magnitude of coastal retreat may be about the same in the two areas where coastal retreat largely provides the mechanism for base level fall steep coastal drainages discharge their debris onto coastal piedmonts benches and the resultant alluvial fans prograde over marine deposits in southern oregon the alluvial fan building episode was relatively short about 2 20 k y in duration fan aggradation ceased as a consequence of fan entrenchment most likely brought on by buildup and steepening of the fan over time

modeling the development of marine terraces on tectonically mobile rock coasts abstract a mathematical model was used to study the effect of glacially induced fluctuations in sea level on the formation of wave cut terraces on tectonically mobile rock coasts two deep water wave sets were used to calculate breaker height and depth which along with surf zone width bottom roughness and the gradient of the submarine slope dictated the force exerted at the shoreline an erosional force threshold was employed to represent the variable strength of the rocks the model also considered tidal range the time that the water level spent at each intertidal elevation and the protective effect of debris accumulation at the cliff foot three hundred runs were made with constant sea level and with different rates of rising and falling relative sea level rates of erosion increased with the rate of rising and falling sea level but eventually decreased in some runs with very rapid changes in relative sea level fifty five longer runs were also made with a quaternary sea level model that consisted of 26 glacial cycles representing the period from 2 million to 0 9 million years ago and nine cycles of approximately twice the amplitude and wavelength in the last 0 9 million years these runs were made on a landmass experiencing slow 0 11 mm yr 1 or fast 0 74 mm yr 1 positive or negative changes in the elevation of the land it was found that on rising landmasses erosional coastal terraces are formed during interglacial stages and on subsiding landmasses during glacial stages the number of terraces increased with the rate of uplift and subsidence and with the slope of the hinterland terrace gradient increased with tidal range and decreased with rock resistance the was an inverse relationship between terrace width and the strength of the rock

late cenozoic to recent transtensional deformation across the southern part of the gaoligong shear zone between the indian plate and se margin of the tibetan plateau and its tectonic origin abstract within the southeastern part of the tibetan plateau the gaoligong shan shear zone forms the boundary between the tengchong and baoshan blocks and is one of the main cenozoic strike slip fault systems of the eastern himalayan syntaxis the mountain ranges rise to a maximum elevation of 3623 m with a width of 20 km and a length of 400 km the core of the shear zone consists of a narrow belt of mylonitic rocks with right lateral strike slip fabrics formed during the northward movement of india relative to eurasia in oligocene and miocene time to the south the mountains decreases in elevation and end against the wanding fault the latter is one of a series of ne sw striking active left lateral strike slip faults within the southeastern part of the tibetan plateau the cause and timing for the change in elevation of the gaoligong shan is unknown but based on our recent structural and fission track geochronological work the decrease in elevation is the result of east west extension across the southern part of the gaoligong shear zone inferred from the late cenozoic and active normal faults along its eastern and western boundaries southward the eastern boundary fault system merges with a series of splays of the wanding strike slip fault while the western boundary fault system is bent into parallelism with the wanding fault this geometric relationship suggests that the normal faulting along the eastern and western boundary of the gaoligong shear zone was caused by transfer of the ne sw left lateral movement along the wanding fault into e w extension on faults to the northeast the resultant normal faulting caused the lowering of the topography in the southern part of the shear zone fission track data from 11 samples from the mylonitic rocks in the footwall of the ruili oblique slip fault left lateral thrust slip yielded ages between 8 4 and 0 9 ma coeval with volcanism within the jietou and mangbang basins the left lateral strike slip movement along the wanding and ruili faults is interpreted to have accommodated differential clockwise rotation of the gaoligong shear zone and its adjacent tectonic units during late cenozoic to recent time during the northward movement of the indian plate with respect to the southeastern margin of the tibetan plateau along the right lateral sagaing fault

the horizontal kinetic energy spectrum and spectral budget simulated by a high resolution troposphere stratosphere mesosphere gcm abstract horizontal kinetic energy spectra simulated by high resolution versions of the geophysical fluid dynamics laboratory skyhi middle atmosphere general circulation model are examined the model versions considered resolve heights between the ground and 80 km and the horizontal grid spacing of the highest resolution version is about 35 km tropospheric kinetic energy spectra show the familiar 3 power law dependence on horizontal wavenumber for wavelengths between about 5000 and 500 km and have a slope of 5 3 at smaller wavelengths qualitatively similar behavior is seen in the stratosphere and mesosphere but the wavelength marking the transition to the shallow regime increases with height taking a value of 2000 km in the stratosphere and 4000 km in the mesosphere the global spectral kinetic energy budget for various height ranges is computed as a function of total horizontal wavenumber contributions to the kinetic energy tendency from nonlinear advective processes from conversion of avai

modeling the development of wave cut shore platforms abstract a mathematical model was used to investigate the development of wave cut shore platforms with constant sea level the model considered the effects of deep water wave height spectra period and wavelength breaker height and depth breaker type the width and bottom roughness of the surf zone the gradient of the submarine slope an erosional threshold related to the strength of the rocks the number of hours each year in which the water level is at each intertidal elevation and the amount and persistence of the debris at the cliff foot intertidal erosion rates were calculated according to the force of the surf reaching the shoreline whereas submarine erosion rates were determined using a depth decay variable each of the two hundred and fifty model runs consisted of 300 000 iterations platform width increased and gradient progressively decreased through model runs and states of static equilibrium were attained by the end of one hundred and nine runs when the wave induced force at each point in the intertidal zone had became too weak to continue eroding the rock runs with mesotidal spring tidal range 3 m generally produced subhorizontal platforms with cliff platform junctions at the mean low water neap tidal level a greater variety of profiles was produced in runs with macrotidal spring tidal ranges 9 m although almost 30 of these runs produced gently sloping platforms with average gradients of only 0 3 about two thirds of the simulated profiles had average gradients ranging from about 1 to 3 simulated platform width increased with tidal range and decreased with the rate of submarine erosion rock resistance the roughness or irregularity of the platform surface the amount and persistence of the cliff foot debris and wave period because higher waves break in deeper water than lower waves there was no consistent relationship between simulated platform width and wave height

microbial reduction of fe iii in illite smectite minerals by methanogen methanosarcina mazei abstract clay minerals are ubiquitous in soils sediments and sedimentary rocks and could coexist with methanogens in anoxic environments but whether or not methanogens can reduce structural fe iii in clay minerals other than smectite is not known the objective of this study was to understand the capability of a mesophilic methanogen methanosarcina mazei in reducing structural fe iii in illite smectite clay minerals and its potential role in inducing mineralogical changes bioreduction experiments were performed in batch systems where four different clay minerals nontronite nau 2 mixed layer illite smectite rar 1 and iscz 1 and illite imt 1 were exposed to m mazei in growth medium with and without anthraquinone 2 6 disulfonate aqds as electron shuttle the extent and rate of bioreduction were quantified via wet chemistry and mineralogical transformed by x ray diffraction and scanning and transmission electron microscopy our results demonstrated that m mazei was able to reduce structural fe iii in clay minerals with fe iii in smectite being the most reducible and illite the least aqds enhanced the reduction rate and extent the bioavailability of structural fe iii to m mazei was correlated to the smectite proportion in each clay mineral methanogenesis was inhibited by fe iii bioreduction possibly due to diversion of electrons from the methanogenesis pathway to structural fe iii in clay minerals bioreduction of fe iii in clay minerals induced formation of biogenic mixed layer illite smectite silica and vivianite these data collectively showed that mesophilic methanogen is capable of reducing structural fe iii in illite smectite minerals and of inducing a number of mineralogical changes

magmatic eruptions and iron volatility in deep sea hydrothermal fluids author s pester nj ding k seyfried we abstract during periods of volcanic activity hydrothermal fluid chemistry changes drastically becoming unusually dilute due to enhanced degrees of phase separation despite decreases in nearly all other metals these dilute fluids maintain surprisingly high dissolved fe concentrations this is demonstrated by a 17 yr time series from 9 50 n on the east pacific rise where two eruption cycles are separated by a decade of steady state chemical and physical conditions we report experimental data confi rming a sharp increase in fe solubility in low salinity and low density vapors that constitutes a reversal in behavior exhibited in near critical vapors characteristic of the steady state condition in accordance with field observations during the eruptions a fundamental divergence between the otherwise similar behaviors of fe and mn also results this helps explain how fe fluxes are maintained during magmatic events which may have important implications for the succession and temporal evolution of vent related fauna calibrated geochemical proxies for subseafl oor reaction conditions pressure temperature now allow us to elucidate hydrothermal processes from steady state through eruptive and recovery stages at the 9 50 n system 2014 geological society of america

restratification at a california current upwelling front part i observations abstracta coordinated survey between a subsurface lagrangian float and a ship towed triaxus profiler obtained detailed measurements of a restratifying surface intensified front above 30 m within

reduction of structural fe iii in nontronite by thermophilic microbial consortia enriched from hot springs in tengchong yunnan province china abstract iron redox cycling provides one of the most important energy sources supporting microorganisms in terrestrial hot springs in order to understand microbial fe iii reduction processes in hot springs fe iii reducing bacterial consortia were successfully retrieved from seven acidic hot springs in tengchong county yunnan province china a temperature range from 40 6 c to 74 7 c and a ph range from 2 64 to 4 72 these fe iii reducing consortia were mainly composed of sulfate reducing bacteria srb including desulfotomaculum thermodesulfobacterium and desulfomicrobium and organic matter fermenting bacteria thermoanaerobacterium and thermoanaerobacter with each consortia having specific composition depending on the physio chemical conditions of the studied hot springs the obtained consortia were capable of dissimilatory reduction of fe iii in nontronite nau 2 ferruginous smectite with 20 8 to 29 8 reduction extent and initial reduction rate of 0 011 0 023 mm fe iii g nau 2 h these extents and rates were comparable to those by mesophilic fe reducers in the presence of electron shuttles both high temperature and the possible presence of electron shuttles in hot springs may have accounted for these observed high reduction extents and rates various secondary minerals formed during nau 2 bioreduction including fe sulfides and oxides silicates and silica in one spring illitization and kaolinization of smectite were observed suggesting that fe reducers play important roles in mineral transformation in geothermal environments

development of shore platforms on kaikoura peninsula south island new zealand ii the role of subaerial weathering the role of subaerial weathering in the development of shore platforms on kaikoura peninsula is investigated evidence for weathering came from a number of distinctive surface morphologies on platforms salt crystal growth water layer weathering and slaking schmidt hammer test data showed that weathering had occurred and that rock strength was reduced through weathering by as much as 50 weathering processes on shore platforms rely on repeated wetting and drying and for this reason the number of wetting and drying cycles was estimated it was found that the number of wetting and drying cycles depend not only on the pattern of tidal water levels but also on algae growth and desiccation the number of cycles ranged from 104 to 379 per year at elevations low in the tide range fewer cycles occurred the greatest number occurring between the peaks of spring and neap tides and where rainfall adds to the number the zone of most cycles was estimated to occur between 0 6 and 0 9 m above mean sea level on the more landward margins of platforms it is at these elevations that the highest rates of erosion occur based on these results it is argued that the development of shore platforms at kaikoura results from subaerial weathering caused by repeated wetting and drying this is contrary to the view that shore platforms result from marine erosion

geographical variability of the first baroclinic rossby radius of deformation global 1 83 18 climatologies of the first baroclinic gravity wave phase speed c1 and the rossby radius of deformation l1 are computed from climatological average temperature and salinity profiles these new atlases are compared with previously published 5 83 58 coarse resolution maps of l1 for the northern hemisphere and the south atlantic and with a 1 83 18 fine resolution map of c1 for the tropical pacific it is concluded that the methods used in these earlier estimates yield values that are biased systematically low by 5 15 owing to seemingly minor computational errors geographical variations in the new high resolution maps of c1 and l1 are discussed in terms of a wkb approximation that elucidates the effects of earth rotation stratification and water depth on these quantities it is shown that the effects of temporal variations of the stratification can be neglected in the estimation of c1 and l1 at any particular location in the world ocean this is rationalized from consideration of the wkb approximation

visible near infrared and middle infrared spectroscopy of altered basaltic tephras spectral signatures of phyllosilicates sulfates and other aqueous alteration products with application to the mineralogy of the columbia hills of gusev crater mars 1 we studied visible to near infrared vnir 0 35 2 5 m and middle infrared mir 1800 250 cm 1 also called thermal infrared and vibrational spectra of basaltic tephras from mauna kea volcano that were altered under ambient hydrothermal hydrolytic and acid sulfate and dry heat conditions although models of mir spectra of altered tephras generally produce fits whose quality is reduced compared to deconvolutions of primary lithologies they successfully identify major alteration phases cristobalite oxide phyllosilicate and sulfate except in palagonites mir spectra of the 1 in spectra of the 500 1000 m fraction only if phyllosilicates are present although mauna kea palagonitic tephra is considered a vnir analog to martian dust comparison of mir altered tephra spectra 45 m fraction to dust spectra retrieved from mars global surveyor and mars exploration rover instruments do not provide good spectral matches the best mir match is a tephra that has a strong plagioclase feldspar transparency feature and was altered under dry high temperature oxidizing conditions this sample is not a vnir analog and is not a process analog but it emphasizes the mineralogical importance of plagioclase feldspar in martian dust no single tephra is a good spectral analog across the vnir and mir we found no evidence for substantial sulfates or phyllosilicates in mini thermal emission spectrometer mini tes spectra from gusev crater

estimated global hydrographic variability an estimate is made of the three dimensional global oceanic temperature and salinity variability omitting the seasonal cycle both as a major descriptive element of the ocean circulation and for use in the error estimates of state estimation historical hydrography recent data from the world ocean circulation experiment and argo profile data are all used root mean square vertical displacements in the upper 300 m of the ocean are generally smaller than 50 m except in energetic boundary currents and in the north atlantic subpolar gyre variability in temperature and salinity is strongly correlated below the top 100 m salinity contributions to sea surface height variability appear more significant at low latitudes than expected possibly resulting from advective and diffusive processes results are generally consistent with altimetric variability under two simple kinematic hypotheses and much of the observed structure coincides with known dynamical features a large fraction of the sea surface height variability is consistent with the hypothesis of dominance of the first baroclinic mode

potential shoreline changes induced by three dimensional bathymetric anomalies with gradual transitions in depth abstract the development of an analytic model for nearshore wave propagation and shoreline change shoreward of a bathymetric anomaly is presented the three dimensional 3 d step model bender c j dean r g 2003 wave transformation by axisymmetric 3 dimensional bathymetric anomalies with gradual transitions in depth in review coastal engineering propagates a linear wave field in a region of uniform depth over an axisymmetric bathymetric anomaly to a region representing the nearshore zone the bathymetric anomaly is represented by a series of steps which can approximate uniform or nonuniform slopes this paper presents the development and application of an approximate shallow water analytic shoaling and refraction method analytic s r model which establishes the breaking wave height and angle for arbitrary nearshore slopes thus extending the 3 d step model to the nearshore region where the depth is nonuniform the 3 d step model determines the wave transformation caused by the processes of wave refraction diffraction and reflection the wave heights and directions for transects located shoreward of the bathymetric anomaly are combined with the analytic s r model to determine the wave propagation in a nearshore zone of arbitrary slope employing the shoreline change model calculates the longshore transport and shoreline evolution for the nearshore shoaled and refracted wave field that occurs shoreward of the anomaly through the methods developed in this paper the wave transformation nearshore shoaling and refraction longshore transport and shoreline evolution induced by a 3 d bathymetric anomaly with gradual transitions in depth are investigated comparisons of the analytic nearshore shoaling model with a numerical model verify the results for several bathymetries including both pits and shoals the analytic shoreline change model predicts shoreline response for areas shoreward of bathymetric anomalies comparison to the laboratory experiment of horikawa et al horikawa k sasaki t and sakuramoto h 1977 mathematical and laboratory models of shoreline change due to dredged holes journal of the faculty of engineering the university of tokyo xxxiv no 1 pp 49 57 indicates the shoreline change model is able to predict the equilibrium planform shoreward of a pit when the transport caused by the gradient in breaking wave height is included the results demonstrate the importance of the longshore transport term driven by the gradient in breaking wave height

towed thermistor chain observations of fronts in the subtropical north pacific a thermistor chain was towed 1400 km through the eastern north pacific subtropical frontal zone in january 1980 the observations resolve surface layer temperature features with horizontal wavelengths of 0 2 200 km and vertical scales of 10 70 m the dominant features which have horizontal wavelengths of 10 100 km amplitudes of 0 2 1 0 c and random orientation likely arise from baroclinic instability associated with them is a plateau below 0 1 cpkm in the horizontal temperature gradient spectrum strong temperature fronts o 1 2 c 3 10 km are observed near 33 n 31 n and 27 n temperature variability is partially density compensated by salinity with the fraction of compensation increasing northward there is evidence of vertical mixing during high winds temperature at 15 m depth is roughly normally distributed around the climatological surface mean with a standard deviation of approximately 0 5 c the standard deviation would correspond to an adiabatic meridional displacement of 80 100 km in the mean gradient horizontal temperature gradient at 15 m depth has maximum values in excess of 0 25 c 100 m and kurtosis near 80 in the band 0 10 1 cpkm the 15 m gradient spectrum is inversely proportional to wave number consistent with predictions from geostrophic turbulence theory while the spectrum at 70 m depth has additional variance that is consistent with garrett munk internal wave displacements

modelling the effect of waves weathering and beach development on shore platform development a mathematical model was used to study shore platform development mechanical wave erosion was dependent on such variables as tidal range wave height and period breaker height and depth breaker type surf zone width and bottom roughness submarine gradient rock resistance and the elevational frequency of wave action within the intertidal zone also included were the effects of sand and pebble accumulation cliff height and debris mobility and downwearing associated with tidal wetting and drying the occurrence location and thickness of beaches often depended on initially quite minor variations in platform morphology but owing to their abrasive or protective effect on underlying rock surfaces they were able to produce marked differences in platform morphology generalizations are difficult but the model suggests that platform gradient increases with tidal range platform width also increases with tidal range with slow downwearing but it decreases with fast downwearing platform gradient decreases and width increases with wave energy and decreasing rock resistance and platform roughness with low tidal range platform gradient is generally lower and platform width greater with beaches of fine sand than with gravel but the relationship is more variable with a high tidal range platform width increases and platform gradient decreases with the rate of downwearing on bare surfaces particularly in low tidal range environments but the pattern is less clear on beach covered platforms platforms with large amounts of beach sediment tend to be narrower and steeper than bare platform surfaces platform gradient increases and platform width decreases with increasing cliff height and with decreasing cliff debris mobility copyright 2005 john wiley sons ltd

parameterization of mixed layer eddies part i theory and diagnosis ageostrophic baroclinic instabilities develop within the surface mixed layer of the ocean at horizontal fronts and efficiently restratify the upper ocean in this paper a parameterization for the restratification driven by finite amplitude baroclinic instabilities of the mixed layer is proposed in terms of an overturning streamfunction that tilts isopycnals from the vertical to the horizontal the streamfunction is proportional to the product of the horizontal density gradient the mixed layer depth squared and the inertial period hence restratification proceeds faster at strong fronts in deep mixed layers with a weak latitude dependence in this paper the parameterization is theoretically motivated confirmed to perform well for a wide range of mixed layer depths rotation rates and vertical and horizontal stratifications it is shown to be superior to alternative extant parameterizations of baroclinic instability for the problem of mixed layer restratification two companion papers discuss the numerical implementation and the climate impacts of this parameterization

interpreting energy and tracer spectra of upper ocean turbulence in the submesoscale range 1 200 km submesoscale 1 200km wavenumber spectra of kinetic and potential energy and tracer variance are obtained from in situ observations in the gulf stream region and in the eastern subtropical north pacific in the gulf stream region steep kinetic energy spectra at scales between 200 and 20km are consistent with predictions of interior quasigeostrophic turbulence theory both in the mixed layer and in the thermocline at scales below 20km the spectra flatten out consistent with a growing contribution of internal wave energy at small scales in the subtropical north pacific theenergyspectraareflatterand inconsistentwith predictionsofinteriorquasigeostrophic turbulence theory the observed spectra and their dependence on depth are also inconsistent with predictions of surface quasigeostrophic turbulencetheoryfortheobservedoceanstratification itappearsthatunbalancedmotions most likely internal tides at large scales and the internal wave continuum at small scales dominate the energy spectrum throughout the submesoscale range spectra of temperature variance along density surfaces which are not affected by internal tides are also inconsistent with predictions of geostrophic turbulence theories reasons for this inconsistency could be the injection of energy in the submesoscale range by small scale baroclinic instabilities or modifications of the spectra by coupling between surface and interior dynamics or by ageostrophic frontal effects

holocene emerged notches and tectonic uplift along the jalisco coast southwest mexico this paper presents the preliminary results from a study of holocene emerged shorelines marine notches and their tectonic implications along the jalisco coast the pacific coast of jalisco sw mexico is an active tectonic margin this coast has been the site of two of the largest earthquakes to occur in mexico this century the 1932 mw 8 2 jalisco earthquake and the 1995 mw 8 0 colima earthquake measurement and preliminary radiocarbon dating of emergent paleoshorelines along the jalisco coast provide the first constraints upon the timing for tectonic uplift along this coastline uplifted holocene marine notches and wave cut platforms occur at elevations ranging from ca 1 to 4 5 m amsl in situ intertidal organisms dated with radiocarbon the first ever reported for the jalisco area provide preliminary results that record tectonic uplift during at least the past 1300 years bp at an average rate of about 3 mm year we propose a model in which coseismic subsidence produced by offshore earthquakes is rapidly recovered during the postseismic and interseismic periods the long term period is characterized by slow tectonic uplift of the jalisco coast we found no evidence of coastal interseismic and long term subsidence along the jalisco coast

beach etching and shore platforms etch forms are widely recognised in continental landscapes but little attention has been given to the etch factor in the coastal context evidence mainly from south australia and the iberian peninsula is cited of weathering fronts fortuitously located within the tidal zone and exposed by the stripping of a regolith by waves in addition the possible effects of beach etching or weathering by waters retained by beach sediments are discussed such weathering is difficult to prove in detail but circumstantial evidence from south australian sites suggests it contributes to the development of shore platforms as well as to cliff foot depressions and an assemblage of minor forms such as basins rock doughnuts and fonts the zonation of basins and gutters noted on some coasts may also and in part reflect beach etching

surface swelling of coastal bedrock on inter tidal shore platforms kaikoura peninsula south island new zealand this paper reports the occurrence of swelling of coastal bedrock measured with a traversing micro erosion meter tmem on inter tidal mudstone and limestone shore platforms while numerous micro erosion meter mem studies have been made only a small number have reported surface swelling during this study 24 055 measurements were made with a tmem of those 4047 indicated swelling or 17 of the total number of measurements vertical swelling of up to 8 9 mm was measured and values of 3 and 4 mm were common swelling displayed a complex pattern with minor swelling being superimposed on longer period episodes duration of swelling events in excess of 697 days were recorded while other events were commonly in the order of 3 to 4 months there is a distinct seasonal variation with greater and more frequent swelling occurring during summer months compared with winter explanation for swelling includes the growth of salt crystals in rock lattices and expansion from wetting and drying warm summer temperatures provide the best conditions for both processes swelling appears to be an important precursor to erosion of material from shore platform surfaces the conclusion drawn is that subaerial weathering makes an important contribution to the lowering of the shore platforms on the kaikoura peninsula

thermohaline variability in the upper ocean the main goal of this exploratory study is to determine how the temperature salinity relationship changes with horizontal length scale and depth in the ocean temperature and salinity were measured on a range of scales from 4 m to 1000 km towing a seasoar along isobars and isopycnals in the subtropical gyre of the north pacific during the winter of 1997 the wavelet transform technique is used to compute the horizontal density ratio and thermohaline variability as a function of scale and location measurements along an isobar in the mixed layer show that the horizontal density ratio is 1 at all scales observed that is horizontal temperature and salinity gradients tend to cancel each other in their effect on density thermohaline variability at small scales is intermittent and clusters around large scale thermohaline anomalies below the base of the mixed layer horizontal gradients of temperature are only partially opposed by salinity and the density ratio is close to 2 in the thermocline the distribution of thermohaline variability is uniform along isobars but intermittent and colocated at different scales along isopycnals density compensated variability ubiquitous in the mixed layer is reduced along deeper isopycnals compensation of horizontal temperature and salinity gradients supports recent theoretical ideas that mixing in the winter mixed layer depends on horizontal density gradients

unraveling complex 2 μm clay mineralogy from soils using x ray diffraction profile modeling on particle size sub fractions implications for soil pedogenesis and reactivity a specific methodology was developed to refine the complex clay mineralogy commonly encountered in soil environments the soil examined was a cambisol developed into a ferralitic paleosol the sample was split into four sub fractions of different particle sizes 0 05 0 05 0 1 0 1 0 2 and 0 2 2 mu m and their respective mass contributions to the overall 2 mu m clay fraction were determined for each sub fraction x ray diffraction xrd patterns were modeled using a trial and error approach based on the direct comparison of experimental and calculated profiles quantitative information derived from the fitting procedure for the different sub fractions allowed for the determination of the complex mineralogy of the 2 mu m clay fraction through the identification and quantification of eight clay phases the results show that the finest and most reactive clay fraction 0 05 pm was totally hidden in the xrd pattern of the 2 mu m fraction the fraction commonly considered in soil mineralogical analyses similarly this procedure revealed the presence of illite smectite chlorite and kaolinite illite mixed layer minerals seldom described in soil literature using classical methods the use of this methodology improved our understanding of the pedogenesis of this soil through the identification and quantification of clay phases structural properties the analysis of the evolution of structural parameters with particle size allowed for the detection of local modifications in the interlayer composition of expandable and hydroxy interlayered vermiculite layers following this approach key information can be derived to determine subtle changes in clay mineralogical composition that are related to microorganism and or plant activity

mesoscale spectrum of atmospheric motions investigated in a very fine resolution global general circulation model 1 the horizontal spectrum of wind variance conventionally referred to as the kinetic energy spectrum is examined in experiments conducted with the atmospheric gcm for the earth simulator afes global spectral general circulation model we find that the control version of afes run at t639 horizontal spectral resolution simulates a kinetic energy spectrum that compares well at large scales with global observational reanalyses and at smaller scales with available aircraft observations at near tropopause levels specifically there is a roughly 3 power law dependence on horizontal wave number for wavelengths between about 5000 and 500 km transitioning to a shallower mesoscale regime at smaller wavelengths this is seen for both one dimensional spectra and for the two dimensional total wave number spectrum based on a spherical harmonic analysis the simulated spectrum at midtropospheric levels is similar in that there is a transition to a shallower mesoscale regime but the spectrum in the mesoscale is clearly steeper at midtroposphere than near the tropopause there seem to be no extensive observations of horizontal spectra available in the midtroposphere so it is not known whether the contrast seen in the model between upper and mid tropospheric levels is realistic the dependence of the model simulated variability on the subgrid scale moist convection parameterization is examined the space time variability of rainfall is shown to depend strongly on the convection scheme employed the tropospheric kinetic energy spectrum in the mesoscale seems to be correlated with the precipitation behavior so that in a version with a more variable precipitation field the kinetic energy in the mesoscale is enhanced this suggests that the mesoscale motions in the model may be directly forced to a significant extent by the variability in the latent heating field experiments were also performed with a dry dynamical core version of the model run at both t639 and t1279 resolutions this version also simulated a shallow mesoscale range supporting the view that the mesoscale regime in the atmosphere is energized at least in part by a predominantly forward i e downscale nonlinear spectral cascade experiments with various formulations of the hyperdiffusion horizontal mixing parameterization show that the kinetic energy spectrum over about the last half of the resolved wave number range is under strong control by the parameterized mixing however the t1279 model simulates almost a decade of the shallow mesoscale regime i e for horizontal wavelengths from about 80 to 500 km that appears to be fairly independent of the diffusion employed finally experiments are conducted in the dry version to see the effects on the kinetic energy spectrum of changing the thermal rossby number for the simulations

hydrothermal clay mineral formation of east pacific rise and bauer basin sediments samples of surface metalliferous sediment recovered from the crest of the east pacific rise at 6 s and 10 s latitudes and from the adjacent bauer basin are characterized by an authigenically formed fe rich montmorillonite that dominates the non carbonate mineralogy of the clay fraction 2 m oxygen isotopic formation temperatures indicate that the fe montmorillonites are created by low temperature hydrothermal processes 30 50 c in the 10 s region of the east pacific rise and bauer basin possibly as a result of cooling and oxidation of unstable high temperature 380 30 c sulfide assemblages or as a result of the percolation of hydrothermally altered seawater solutions through underlying basalt and sediments the widespread sedimentation of the clay mineral is suggested to be caused by colloidal transport possibly as a result of erosion of hydrothermal mounds by bottom currents hydrothermal fe montmorillonite nontronite formation may act as a direct and significant oceanic sink for si and fe released by the high temperature hydrothermal alteration of basalt at ocean spreading centers

geostrophic adjustment and restratification of a mixed layer with horizontal gradients above a stratified layer abstract the restratification of a mixed layer with horizontal density gradients above a stratified layer is considered solutions are obtained on the assumption that the width across this front is much larger than the local radius of deformation bh f based on the buoyancy change across the front b mean mixed layer depth rdh and the coriolis parameter f where b is defined as rd g 0 0 but the fractional change in the mixed layer depth is not required to be small for an initially quiescent mixed layer created by homogenizing a fluid of constant stratification to a depth that varies horizontally the isopycnals in the mixed layer tilt about their intersections with the top surface in the adjusted state and the base of the mixed layer flattens slightly in the frontal region other cases considered include mixed layer fronts with initial momentum out of geostrophic balance created by vertical mixing of a layer with horizontal gradients previously in thermal wind balance for a wide front the

postglacial sea level rise and sedimentary response in the guadiana estuary portugal spain border abstract the study of sedimentological features foraminifera and molluscan fauna in samples recovered from four rotary boreholes permitted after 14 c dating the first assessment of the post glacial transgression in guadiana river estuary the holocene sequence is underlain by coarse sediments from delta fan enclosing continental swamp deposits dated 16 980 year bp the holocene sedimentary sequence was deposited either directly on this delta fan gravels or on top of fluvial sands deposited probably between 11 000 and 10 000 yr bp an accelerated phase of the estuary infilling by clayey sediments containing the salt marsh foraminifer trochammina began ca 9800 year bp when sea level was about 39 m below present between 7500 and 7000 year bp the central part of the estuary started to accommodate coarser sediments partially introduced from the continental shelf the first phase of holocene sea level rise at a rate of 0 85 m century terminated ca 6500 year bp since then lagoonal sediments in the vicinity of the estuary have been enclosed behind sand spits and predominantly sandy sedimentation was initiated within the estuary after a second phase of slower rise at the rate of 0 3 m century which lasted until ca 5000 year bp the sea approached the present level

marine notches in coastal cliffs indicators of relative sea level change perachora peninsula central greece abstract in several sites in the complex faulted western part of perachora peninsula central greece three principal marine notches in rocky coasts are present in each site no holocene notches occur above the upper of the three notches only subaerial weathering affected the rocks lateral variation in the heights of notches demonstrates differential uplift due to fault control and illustrates the complexity of application of marine notches in interpretation of tectonic history the lower undated notch is prominent in places coincides with modern sea level and is interpreted to be forming now it suggests that the western part of the peninsula has been stable for a considerable time the middle and upper notches vary in height between sites and may not be time equivalent but represent earlier sea level positions in the harbour adjacent to the heraion archaeological site the middle and upper notches are preserved in most places as notch roofs so that gradual uplift led to removal of notch floors by physical chemical and biotic processes in exposed locations however within a few hundred metres west of the harbour four uplifted plus a fifth forming now notches have been illustrated by pirazzoli et al tectonophysics 229 1994 201 that cannot be readily correlated to the harbour site and indicate differential uplift by fault displacement in a more complex situation at mylokopi 6 km ne of heraion three different notch profiles occur in three blocks separated by two faults however within the central block of the three two very different profiles are preserved only tens of metres apart beneath one continuous upper notch roof at the same height this complex arrangement interpreted as variability of exposure to marine processes on different parts of this irregular embayment such that one profile containing three notches was controlled largely by abrasion and formed notches that are vertically more extensive while the other profile containing five narrow notches formed by dissolution and or biological erosion at the same time in the protected east end of the block however if only one or the other profile was visible very different tectonic interpretations would result the bedrock of perachora peninsula also shows important variations in resistance to erosion affecting the resulting notch profiles and some sites are influenced by structurally controlled differential subaerial weathering forming ridges and grooves giving the false impression of extra minor notches the distinction between dissolution controlled and structure controlled minor notches may not be possible in some places the interpretations of notch profiles can be highly complex and influence views of tectonic history in a given region overall the occurrence of three principal notches beneath one uplifted notch roof in several sites indicates that a holocene uplift rates outpaced post glacial sea level rise b there were three principal periods of relative sea level stillstand affecting the perachora peninsula and c uplift of the entire western part of the perachora peninsula is an important component of its tectonic processes probably more important than fault movement within the peninsula

beach morphodynamics in a strong wind bay a low energy environment abstract the morphodynamic behaviour of a multibarred beach in a fetch limited strong wind bay seaford beach se australia was examined during both high and low energy conditions and considered in the context of a definition of low energy provided in the literature measurements of nearshore waves currents and morphology revealed a bimodal behaviour under initial low energy conditions the beach exhibited a low tide terrace state and waves and currents were of very low magnitude during subsequent high energy conditions the beach demonstrated dynamic behaviour through the formation of a transitional transverse bar and rip rhythmic bar and beach and migration of the middle bar with the morphology remaining in an arrested high energy state during intervening low energy periods although broadly conforming to the morphodynamic model the beach did exhibit some distinct characteristics attributable to its fetch limited location limited progression through the morphodynamic model and the importance of wind direction and magnitude in governing morphodynamic behaviour furthermore rip currents were not significant in driving beach change through intermediate states the presence of infragravity energy in the storm wave spectra a dissipative multibarred surf zone dynamic inner and middle bars and the attainment of a transitional transverse bar and rip rhythmic bar and beach state during rising wave conditions underline seaford beach as bimodal exhibiting process and morphologic features of both higher and lower energy beaches as an example of a beach in a strong wind bay seaford illustrates that not all fetch limited beaches are low energy furthermore the presence of infragravity energy in a highly fetch limited environment indicates that infragravity energy may occur commonly in fetch limited environments that are subject to periodic strong winds a process that has remained largely unrecognised

evolution and inheritance of a rock coast western galicia northwestern spain there is increasing evidence that shore platforms and other elements of rock coasts may be inherited at least in part from interglacial stages when sea level was similar to today s most of this evidence which includes ancient beaches and datable terrestrial deposits has been obtained from areas of resistant slowly eroding rock where the platforms often appear to be much too wide to have developed since the sea reached its present level it is much more dif cult to demonstrate that inheritance has occurred in areas of weaker rock which generally lack any datable material the coast of western galicia in northwestern spain has shore platforms in igneous and metamorphic rocks that were deeply weathered during the tertiary these platforms are closely associated with ancient beaches from the last interglacial stage and associated periglacial and uvio nival deposits that covered and fossilized most of the eemian platforms and cliffs during the late middle and late weichselian glacial stage the sedimentary processes and the thickness and facies of the sediments were determined by the height aspect and gradient of the coastal mountains and their distance from the coast radiocarbon dating sedimentary analysis and platform morphology indicate that the shore platforms of galicia have been inherited from at least the last interglacial stage they were fossilized in places beneath thick weichselian deposits and then exhumed during the holocene transgression the abundant evidence for inheritance in galicia has important implications for other coasts in fairly weak rocks where such evidence is generally lacking copyright 2003 john wiley sons ltd

development of shore platforms on kaikoura peninsula south island new zealand abstract the role of waves in shore platform development has been investigated on kaikoura peninsula by direct measurement of waves in deep water and on platforms at high tide this showed that the deepwater wave environment off the kaikoura peninsula is very energetic but the amount of energy delivered to platforms is very low in deep water wave power ranged from 5900 to 106 700 n m s 1 per m of crest when calculated from mean significant wave height and when calculated from maximum wave height it ranged from 31 400 to 5 370 000 n m s 1 per m of crest a comparison of deep water wave energy flux with wave energy flux at the high tide cliff of platforms showed that there was a reduction by as much as five orders of magnitude during storm conditions an analysis of the role of breaking waves revealed that these are ineffective as an erosional agent because the depth of water offshore causes breaking before waves arrive on platform surfaces depth of water controlling wave breaking causes larger storm waves to break further from shore preventing direct attack at the cliff base shear stresses and dynamic forces under waves were calculated from waves measured on shore platforms this showed that these forces never exceeded the compressive strength of the platform rocks at kaikoura it is concluded that wave forces are not directly capable of causing erosion on shore platforms at kaikoura

sub mesoscale lateral density structure in the oceanic surface mixed layer 1 we investigate the horizontal scales of density variability in the surface mixed layer sml in the north pacific subtropical front stf during a period of highly variable atmospheric forcing wavelet analysis shows that horizontal density variability is not restricted to scales l 10 km as previously suggested but extends to l 2 km the limiting l varies strongly with location and corresponds to a local internal rossby radius that accounts for transient stratification above the seasonal thermocline density compensation in the sml achieved when temperature and salinity effects cancel in their effect on density occurs at 30 n at the climatological front associated with the northern boundary of the stf where large thermohaline gradients are observed at 28 n however temperature gradients within the sml are not compensated by salinity and horizontal density gradients result in 2 l 10 km our observations suggest dynamic processes restratify the sml at scales rarely resolved by numerical models of the sml

rock coasts with particular emphasis on shore platforms rock coasts are one of the most common elements of the world s littoral zone and they are often important sources of sediment for estuaries and beaches economic development growing populations and the potential effects of rising sea level provide a practical need to understand the dynamics of these coasts although there have been significant advances in our understanding of rocky coastal systems further progress has been hindered by a lack of researchers and by the often imperceptible changes that generally occur within human time scales this paper reviews rock coast processes and landforms in a variety of morphogenic environments one of our most fundamental challenges is to determine the degree to which rock coasts are contemporary rather than inherited features from the quaternary when changes in sea level and climate were responsible for marked variations in the nature intensity and elevational distribution of the marine and subaerial processes that sculpture rock coasts

rapid changes in mixed layer stratification driven by submesoscale instabilities and winds 1 submesoscale eddies generated by baroclinic instability of upper ocean fronts lead to rapid restratification of the mixed layer on a time scale of days this restratification can be opposed by a down front wind stress acting in the direction of the geostrophic velocity that drives a surface ekman flow from the dense side to the light side of the front to arrest the slumping of isopycnals a scaling diagnostic is suggested to determine whether the effect of eddies or wind dominates under different conditions using a numerical model we investigate the juxtaposition of submesoscale eddies and down front winds acting on the mixed layer by estimating the eddy induced overturning stream function in the mixed layer we separate the along and cross isopycnal fluxes of buoyancy associated with submesoscale mixed layer eddies and demonstrate the need for parameterization of the advective along isopycnal flux though the cross front transport of buoyancy induced by the down front component of the wind opposes restratification by mixed layer eddies it becomes diminished as the eddies and growth of the frontal instability disrupt alignment between the wind and frontal axis

where is the seaward edge a review and definition of shore platform morphology abstract shore platforms are erosional coastal landforms that have attracted scientific attention since the mid 19th century the defining element of a platform is width that is used in many calculations such as determining a platform s evolutionary state or inferring how wave energy is distributed along the shore although a critical variable there are no uniform criteria for defining the seaward edge quantification of platform width has been driven by site specific variables with the seaward edge defined on the basis of tides morphology biology processes and sediment coverage the lack of a uniform definition has meant that comparative studies are difficult and results are possibly spurious as widths derived from very different criteria can vary by an order of magnitude just on the basis of which criteria is used to determine its edge in this review a combination of morphologic and process elements is used to define the seaward edge of a shore platform the development of strict criteria is especially needed in an environment of rising sea levels if measurements of landscape change are to be made in addition the advent of seamless datasets that cross the land sea boundary means that the delineation of platform morphology is no longer limited by physical access this review concludes that the seaward edge of a shore platform will occur at or landward of wave base and should be defined as the point where active erosion of the bedrock ceases characterised by erosional features such as notches and block plucking scars or the deposition of sediment of such a thickness that the underlying bedrock is not exposed during storm events

estimates of ocean macroturbulence structure function and spectral slope from argo profiling floats abstractthe argo profiling float network has repeatedly sampled much of the world ocean this study uses argo temperature and salinity data to form the tracer structure function of ocean variability at the macroscale 10 1000 km mesoscale and above here second order temperature and salinity structure functions over horizontal separations are calculated along either pressure or potential density surfaces which allows analysis of both active and passive tracer structure functions using argo data a map of global variance is created from the climatological average and each datum when turbulence is homogeneous the structure function slope from argo can be related to the wavenumber spectrum slope in ocean temperature or salinity variability this first application of structure function techniques to argo data gives physically meaningful results based on bootstrapped confidence intervals showing geographical dependence of the structure functions with slopes near on average independent of depth

a new technique for evaluating short term rates of coastal bioerosion and bioprotection a multi scale and multi method approach has been developed to evaluate the nature and effects of short term biological colonisation this method has been used at falasarna on the western coast of crete to investigate bioprotection and bioerosion on a microtidal rocky coast eighteen blocks of limestone 5 5 2 cm were exposed for 7 months september 1998 to april 1999 at mean sea level at two exposed sites and one sheltered site biological colonization and its impacts were assessed by optical microscopy om scanning electron microscopy sem and multiphoton laser scanning microscopy mplsm exposed sites became colonized more quickly than the sheltered site and once a cover of foliose and filamentous algae had become established bioerosion by cyanobacteria biological etching and chemical weathering were reduced consequently there appears to be an inverse relationship between macroalgal abundance and bioerosion of experimental substrata after 7 months of colonisation thus some level of bioprotection appears to be provided by macro algae under exposed site conditions and would probably become increasingly apparent in longer term research trials

observational evidence of winter spice injection abstract temperature and salinity t s profiles from the global array of argo floats support the existence of spice formation regions in the subtropics of each ocean basin where large destabilizing vertical salinity gradients coincide with weak stratification in winter in these characteristic regions convective boundary layer mixing generates a strongly density compensated sdc layer at the base of the well mixed layer the degree of density compensation of the t s gradients of an upper ocean water column is quantified using a bulk vertical turner angle tub between the surface and upper pycnocline the winter generation of the sdc layer in spice formation zones is clearly seen in argo data as a large amplitude seasonal cycle of tub in regions of the subtropical oceans characterized by high mean tub in formation regions argo floats provide ample evidence of large abrupt spice injection t s increase on subducted isopycnals due to vertical mixing associated with the winter increase in tub a simp

morphological features and processes in the central algarve rocky coast south portugal morphological features along the algarve rocky coast south portugal are identified and described with an emphasis on shore platforms and notches the contributions of processes such as wave attack chemical weathering and bioerosion to sculpting the shore platforms are discussed the preferential localization of shore platforms on sites exposed to waves and the lack of significant chemical weathering point to wave erosion as the first order factor in platform formation whilst bioerosion bioprotection lithology and geological structure determine platform morphological variations in addition platforms above the present intertidal zone appear to have a polygenetic evolution being inherited from former sea level highstands and currently undergoing chemical weathering the occurrence of notch features is independent of the degree of exposure to waves but they mostly occur where the substratum is sand hydrostatic pressure appears to be an important factor in the formation of marine caves in the more sheltered sites

a physical model for the rate of coastal tafoni development to explain the temporal change in growth rates of tafoni on homogeneous insoluble rocks modeling is carried out based on a formulated relationship for weathering induced reduction of rock strength the model is expressed by z z c 1 sqrt t ast t where z is the depth of tafoni z c is the ultimate depth t is the time and t is the time lag application of the model to the pacific coast of japan reveals that 1 the model accurately describes tafoni development 2 average growth rates presented by most previous studies are underestimated and 3 an exponential decrease in growth rates stems from strength reduction by inherent rock weathering

the morphosedimentary behaviour of a headland beach system quantifying sediment transport using fluorescent tracers abstract embayed beaches occurring along rocky coasts with headlands controlling hydrosedimentary processes are considered to be constrained sedimentary systems with little longshore sediment transfer between them such beaches are likely to narrow under rising sea level and a deficit of fluvial sediment and because beaches act to dissipate wave energy cliff erosion is expected to increase knowledge of hydrosedimentary processes in fetch limited environments such as embayed beaches is therefore a fundamental management tool in erosion prone coastal areas such as the algarve region southern portugal the main objective of this work is to quantify longshore sediment transport lst using a sedimentary tracer and compare the results with the ones derived via empirical formulae from several authors to achieve this we establish the spatial and temporal patterns of stained sediment and relate these to marine climate data over six tidal cycles for three adjacent embayed beaches the values of displaced sand estimated using tracer and scaled to mixed layer depth were compared with the results of five well known lst formulae to assess the applicability of each model to mesotidal environments of the lst formulae used the cerc 2013 shows to be the most accurate in our study area this study demonstrates the efficacy of using tracers for tracking and quantifying the sediment transport and as a basis for assessing the viability of different lst formulae for representing transport in these types of environments the work also shows the importance of the morphological control of hydrosedimentary processes including the disruption of longshore drift and the sediment transfer promoted by shore platforms

three dimensional structure and temporal evolution of submesoscale thermohaline intrusions in the north pacific subtropical frontal zone abstract four instances of persistent intrusive deformation of the north pacific subtropical front were tagged individually by a lagrangian float and tracked for several days each feature was mapped in three dimensions using repeat towed observations referenced to the float isohaline surface deformations in the frontal zone included sheetlike folds elongated in the alongfront direction and narrow tongues extending across the front all deformations appeared as protrusions of relatively cold and fresh water across the front no corresponding features of the opposite sign or isolated lenslike structures were observed the sheets were o 10 m thick protruded about 10 km into the warm saline side of the front and were coherent for 10 30 km along the front having about the same thickness and cross frontal extent as the sheets tongues extended less than 5 km along the front all of the intrusions persisted as long as they were followed several days to one week their structures evolved on both inertial

isopycnal mixing suppression by the antarctic circumpolar current and the southern ocean meridional overturning circulation abstractthe meridional overturning circulation moc in the southern ocean is investigated using hydrographic observations combined with satellite measurements of sea surface height a three dimensional spatial and vertical estimate of the isopycnal eddy diffusivity in the southern ocean is obtained using the theory of ferrari and nikurashin that includes the influence of suppression of the diffusivity by the strong time mean flows it is found that the eddy diffusivity is enhanced at depth reaching a maximum at the critical layer near 1000 m the estimate of diffusivity is used with a simple diffusive parameterization to estimate the meridional eddy volume flux this estimate of eddy volume flux is combined with an estimate of the ekman transport to reconstruct the time mean overturning circulation by comparing the reconstruction with and without suppression of the eddy diffusivity by the mean flow the influence of the suppression on the overturning is illuminated it is shown that the suppressio

modeling the effect of late quaternary interglacial sea levels on wave cut shore platforms abstract a mathematical wave erosional model was used to study the effect of high sea levels during the penultimate oxygen isotopic stage 7 and last interglacials substage 5e and in the late holocene stage 1 on the present morphology of wave cut shore platforms sea level was considered to have been either the same as today or 2 25 m lower during the penultimate interglacial and 2 25 4 5 or 6 75 m higher than today during the last interglacial stage the model suggested that inherited gently sloping shore platforms in resistant rocks may be essentially protected today from erosion by high storm waves the lowest platform gradients were in runs with mesotidal 3 m range and usually with low wave periods low surf attenuation rates and weak rocks modern platform gradients increased with the difference in elevation between sea levels during successive interglacial stages shore platforms were widest in runs in which sea level was the same as today in the penultimate interglacial and 4 5 m higher than today during the last interglacial constant sea level and high last interglacial sea levels with considerable overlapping between the zones of high duration values between the mean neap high and low tidal levels in stages 7 5e and 1 were conducive to the development of wide shore platforms whereas sea levels lower than today s in stage 7 tended to produce narrower platforms in general higher sea levels during the last interglacial tended to produce higher cliff platform junctions than constant sea level unless the sea was lower than today during the penultimate interglacial stage there was a lack of supratidal ledges in macrotidal 9 m model runs with high initial gradients this suggests that gently sloping inherited shore platforms are essential for the subsequent development of supratidal nonstructural ledges in high tidal environments during periods of higher sea level intertidal ledges developed in the upper portion of the modern intertidal zone under a variety of tidal and sea level conditions these ledges can develop independently of lithological or structural influences and without any change in sea level a single high sea level may also simultaneously produce two ledges at different supratidal elevations in mesotidal environments

coupling of fe ii oxidation in illite with nitrate reduction and its role in clay mineral transformation abstract in pedogenic and diagenetic processes clay minerals transform from pre existing phases to other clay minerals via intermediate interstratified clays temperature pressure chemical composition of fluids and time are traditionally considered to be the important geological variables for clay mineral transformations nearly ten years ago the role of microbes was recognized for the first time where microbial reduction of structural fe iii in smectite resulted in formation of illite under ambient conditions within two weeks however the opposite process the oxidation of structural fe ii in illite has not been studied and it remains unclear whether or not this process would result in the back reaction e g from illite to smectite the overall objective of this study was to investigate biological oxidation of structural fe ii in illite coupled with nitrate reduction and the effect of this process on clay mineral transformation laboratory incubations were set up where structural fe ii in illite served as electron donor nitrate as electron acceptor and pseudogulbenkiania sp strain 2002 as mediator solution chemistry and gas composition were monitored over time mineralogical transformation resulting from bio oxidation was characterized with x ray diffraction and scanning and transmission electron microscopy our results demonstrated that strain 2002 was able to couple oxidation of structural fe ii in illite with reduction of nitrate to n 2 with nitrite as a transient intermediate this oxidation reaction resulted in transformation of illite to smectite and ultimately to kaolinite illite smectite kaolinite transformations this study illustrates the importance of fe redox process in mediating the smectite illite mineral cycle with important implications for fe redox cycling and mineral evolution in surficial earth environments

parameterization of mixed layer eddies part ii prognosis and impact abstract the authors propose a parameterization for restratification by mixed layer eddies that develop from baroclinic instabilities of ocean fronts the parameterization is cast as an overturning streamfunction that is proportional to the product of horizontal buoyancy gradient mixed layer depth and inertial period the parameterization has remarkable skill for an extremely wide range of mixed layer depths rotation rates and vertical and horizontal stratifications in this paper a coarse resolution prognostic model of the parameterization is compared with submesoscale mixed layer eddy resolving simulations the parameterization proves accurate in predicting changes to the buoyancy the climate implications of the proposed parameterization are estimated by applying the restratification scaling to observations the mixed layer depth is estimated from climatology and the buoyancy gradients are from satellite altimetry the vertical fluxes are comparable to monthly mean air sea fluxes in large areas of

episodic uplift deduced from holocene shorelines in the perachora peninsula corinth area greece four raised shorelines between 1 1 m and 3 5 m have been identified at two localities on the perachora peninsula and were dated by ams 14c to between 6400 and 1500 calibrated years ago uplift movements seem to have occurred in increments of 0 8 0 3 m with a return period of about 1600 years the last uplift coincided with a regional tectonic paroxysm which has already been documented in several areas of the eastern mediterranean the average uplift rate was probably faster during the holocene than the average since the last interglacial period no important vertical displacement occurred in this area at the time of or after the 1981 earthquake but a new episode of coseismic uplift may be in preparation

modelling the quaternary evolution of shore platforms and erosional continental shelves a mathematical model was used to investigate the effect of glacially induced fluctuations in sea level on the evolution of wave cut shore platforms and erosional continental shelves during the quaternary the model used two deep water wave sets which were used to calculate breaker height and depth and the force of the waves at the waterline according to the width and bottom roughness of the surf zone and the gradient of the submarine slope the model also incorporated an erosional threshold related to the strength of the rocks the number of hours each year in which the water level is at each intertidal elevation and the amount and persistence of the debris at the cliff foot most runs were made using a sea level model that consisted of 26 glacial cycles from 2 million to 0 9 million years ago and nine of approximately twice the amplitude and wavelength in the last 0 9 million years the model emphasized the dynamic association between the contemporary intertidal platform and the continental shelf both surfaces trend towards a state of static equilibrium under oscillating sea level conditions when attenuated waves are unable to continue eroding the rock if there has not been enough time to reduce the gradient of the shallower portions of the continental shelf however intertidal shore platforms can be in a temporary though possibly long lasting state of dynamic equilibrium the model suggests that most platforms are at least in part inherited from one or in many cases more interglacial stages when sea level was similar to today s copyright 2001 john wiley sons ltd

comprehensive characterization of elevated coastal platforms in the north iberian margin a new template to quantify uplift rates and tectonic patterns abstract the cantabrian margin at the northern iberian peninsula shows elevated coastal platforms extending from west to east for 200 km these erosional surfaces are several kilometers wide and are bounded inland by a paleoshoreline and towards the sea by the retreating current cliff the origin and evolution of these geomorphologic markers remains controversial one of the main challenges arising from the difficulties in correlating the patchy distribution of the platforms and their variable heights along the margin due to lithological differences local tectonism and varying degrees of preservation with the aim of understanding recent coastal evolution a systematic quantitative gis analysis of lidar elevation models 5 m resolution was carried out along 4 000 km2 of the cantabrian coast between 4 15 w and 7 30 w longitude the coastline runs parallel to the cantabrian mountains which are supported by an orogenic root present only beneath the eastern half of the coastline under study the integration on the gis template of the crust mantle boundary as a controlling factor of landscape development has helped in the understanding of the recent evolution of the coastal platforms and in the interpretation of previously unexplained features of their distribution the two main outcomes of this multiscale approach are 1 the correlation of most of the fragmented rasas as part of an original unique coastal platform along the cantabrian margin and 2 the differentiation of two sectors separated by a highly tectonized area associated to the ventaniella fault the western sector has one main continuous surface showing a 0 08 tilt towards the west sometimes interrupted by local and recent minor faults with net slips of meters to tens of meters the eastern sector has several steps of erosional surfaces spread out at various heights without tilt the ventaniella fault separating both sectors produces an apparent vertical offset of 50 m in the main erosional surface our study shows that this fault also separates two distinct evolutions in the elevation of the coastal platform 1 the western coast which has risen continuously probably in response to a lateral gradient in crustal thickness and 2 the eastern coast where uplift is discontinuous over time since several of these surfaces formed below the main paleoshoreline the cantabrian coast captures the influence that crustal structure has on the expression and evolution of geomorphologic markers at the surface and vice versa landform features at the surface can be very sensitive to differential crustal thickness while responding to the same external and climatic forces in the context of the western european framework our work provides a regional template within which future absolute geochronological dating can be based to improve our knowledge of the recent evolution of the atlantic margins

the effects of altimeter instrument noise on the estimation of the wavenumber spectrum of sea surface height the wavenumber spectrum of sea surface height ssh observed by satellite altimetry was analyzed by xu and fu the spectral shape in the wavelength range of 70 250 km was approximated by a power law representing a regime governed by geostrophic turbulence theories the effects of altimeter instrument noise were assumed insignificant at wavelengths longer than 70 km the authors reexamined the assumption in the study using nearly simultaneous observations made by jason 1 and jason 2 during their cross calibration phase this study found that the white noise level of altimetry measurement was best estimated from the spectral values at wavelengths from 25 to 35 km after removing a white noise level based on such estimate from the ssh spectrum the spectral slope values changed significantly over most of the oceans a keyfinding is that the spectral slopes are generally steeper than k 22 k is wavenumber poleward of the 208 latitudes where flatter spectral slopes in some regions have previously caused problems for dynamic interpretations the new results indicate that the spectral slopes in the core regions of the major ocean current systems have values between the original geostrophic turbulence theory and the surface quasigeostrophic theory the near k 24 spectrum suggests that the sea surface height variability at these wavelengths in the high eddy energy regions might be governed by frontogenesis

tidal wetting and drying on shore platforms an experimental assessment abstract rocks were subjected to wetting and drying cycles with de ionized water under real time conditions using tidal simulators one third of the samples experienced 11 h of exposure and 1 h of inundation over a 12 h tidal cycle representing high tidal conditions one third experienced 6 h of exposure and 6 h of inundation representing mid tidal conditions and one third experienced 1 h of exposure and 11 h of inundation representing low tidal conditions we obtained 324 cores from igneous metamorphic and sedimentary rocks from ontario which were exposed to more than 930 wetting and drying cycles over 16 months we obtained 675 cores and cubes from basalts sandstones and argillites from shore platforms in eastern canada which were exposed to about 700 cycles over 12 months many of the cores and cubes experienced very little to no breakdown particularly those from the igneous and metamorphic rocks of ontario sandstones from a sloping platform in the macrotidal bay of fundy and argillites from a horizontal mesotidal platform in gaspe quebec were the most susceptible rock types with equivalent surface downwearing rates ranging from 0 to 4 mm year 1 the results suggest that downwearing rates decrease with elevation within the intertidal zone probably because rocks require much longer to desorb than to absorb water the experiments demonstrated that wetting and drying can be an important process on shore platforms in some types of rock helping to lower the height and reduce the gradient of sloping macrotidal platforms and to reduce the height of horizontal micro and mesotidal platforms

millennial scale oceanic climate variability off the western iberian margin during the last two glacial periods high resolution palaeoclimate records recovered from the iberian margin in core md95 2040 exhibit large fluctuations in oceanographic conditions over the last 190 ka large scale cooling of the surface ocean is indicated by the presence of the polar planktonic foraminifer neogloboquadrina pachyderma sinistral and in some instances the occurrence of ice rafted debris ird ice rafting episodes were prevalent in both of the last two glacials with greater intensity in stages 2 through 4 than in stage 6 the six youngest heinrich events are well defined during the last glacial but detrital carbonate is absent from heinrich layers hl6 hl5 and hl3 dansgaard oeschger stadial equivalent sub millennial ird deposition events have been detected in particular during stage 3 allowing a good match with the cooling displayed in the greenland ice core gisp2 sea surface temperature off portugal in stage 6 was in general warmer than during the last glacial pointing towards a weaker southward influence of polar water masses ice rafting occurred mainly in mid mis marine isotope stage 6 between 173 and 153 kyr as a group of poorly differentiated short duration quasi continuous events mainly marked by the high abundance of sinistral n pachyderma differences exist in ird composition relative to the last glacial with a reduced canadian derived detrital carbonate component combined with an important contribution of volcanic particles the lower magnitude and higher frequency of these events suggest that the higher temperatures would have induced iceberg waning closer to the source areas

extending the upper temperature limit for life the upper temperature limit for life is a key parameter for delimiting when and where life might have evolved on a hot early earth the depth to which life exists in the earth s subsurface and the potential for life in hot extraterrestrial environments a combination of geological and

sedimentology of rocky shorelines 3 hydrodynamics of megaclast emplacement and transport on a shore platform oahu hawaii abstract megaclasts of well cemented coralgal limestone have been emplaced onto a shore platform by large waves on the north shore of oahu hi emplacement and movements of the largest ca 96 ton megaclast have been dated using aerial photographs hydrodynamic forces at the low submerged shoreline cliff are computed using design wave characteristics based on linear wave theory and experimental results considering the local wave climate and near shore bottom topography force exerted by a tsunami has been estimated based on the 1946 aleutian tsunami the computed forces are evaluated in terms of the initial fracturing along a given failure plane that is required in order for the detachment to occur the analysis shows that tsunami as well as large swell waves are capable of quarrying the megaclast provided that sufficient initial fracturing is present dislodgement and emplacement most likely occurred in a sequence during impact of a single wave on the shoreline cliff swell waves however are seldom capable of emplacing large blocks onto the platform due to their rapid disintegration after breaking so that most blocks quarried from the cliff edge fall back onto the submarine terrace emplacement of large boulders seems to require extreme sea waves with periods longer than storms or north pacific swells usually produce transport mechanisms on the shore platform vary depending on megaclast shape sliding is a common mechanism of transport for larger and irregular megaclasts whereas somewhat smaller and platy megaclasts are occasionally found in overturned positions

characterizing the chaotic nature of ocean ventilation ventilation of the upper ocean plays an important role in climate variability on interannual to decadal timescales by influencing the exchange of heat and carbon dioxide between the atmosphere and ocean the turbulent nature of ocean circulation manifest in a vigorous mesoscale eddy field means that pathways of ventilation once thought to be quasi laminar are in fact highly chaotic we characterise the chaotic nature of ventilation pathways according to a nondimensional filamentation number which estimates the reduction in filament width of a ventilated fluid parcel due to mesoscale strain in the subtropical north atlantic of an eddy permitting ocean model the filamentation number is large everywhere across three upper ocean density surfaces implying highly chaotic ventilation pathways and increases with depth by mapping surface ocean properties onto these density surfaces we directly resolve the highly filamented structure and confirm that the filamentation number captures its spatial variability these results have implications for the spreading of atmospherically derived tracers into the ocean interior