erratum to dynamic recrystallization processes in plagioclase porphyroclasts journal of structural geology 23 2001 1781 1802

holocene sea level change and the emergence of neolithic seafaring in the fuzhou basin fujian china abstract neolithic seafaring across the taiwan strait began approximately 5000 years ago and involved open sea voyages over distances of at least 130 km rapid sea level rise preceded the emergence of open sea voyaging but the possible role of environmental change as a stimulus for the development of seafaring is poorly understood we investigate this problem by presenting a record of holocene sea level change and coastal transformation based on sediment cores obtained from the fuzhou basin on the coast of fujian china the cores are located in direct proximity to archaeological sites of the tanshishan neolithic culture 5000 4300 cal bp which is significant for its similarity to the earliest neolithic cultures of taiwan multiple lines of evidence record the early holocene inundation of the fuzhou basin around 9000 cal bp the mid holocene sea level highstand and the final holocene marine transgression this final transition is precisely documented with ams dates showing the change occurred close to 1900 cal bp our paleogeographic reconstruction shows that a large estuary filled the fuzhou basin during the mid holocene tanshishan and zhuangbianshan two of the major fuzhou basin neolithic sites are located today on hills nearly 80 km from the modern coastline however when the sites were settled around 5500 5000 cal bp the marine transgression had transformed these hills into islands in the upper estuary we suggest that the neolithic era estuary setting together with the lack of land suitable for rice paddy agriculture inhibited intensive food production but favored a maritime orientation and the development of seafaring

dynamics of wave setup over a steeply sloping fringing reef abstracthigh resolution observations from a 55 m long wave flume were used to investigate the dynamics of wave setup over a steeply sloping reef profile with a bathymetry representative of many fringing coral reefs the 16 runs incorporating a wide range of offshore wave conditions and still water levels were conducted using a 1 36 scaled fringing reef with a 1 5 slope reef leading to a wide and shallow reef flat wave setdown and setup observations measured at 17 locations across the fringing reef were compared with a theoretical balance between the local cross shore pressure and wave radiation stress gradients this study found that when radiation stress gradients were calculated from observations of the radiation stress derived from linear wave theory both wave setdown and setup were underpredicted for the majority of wave and water level conditions tested these underpredictions were most pronounced for cases with larger wave heights and lower still water levels i e cases with the greatest setdow

wave transformation and wave driven flow across a steep coral reef observations of waves setup and wave driven mean flows were made on a steep coral forereef and its associated lagoonal system on the north shore of moorea french polynesia despite the steep and complex geometry of the forereef and wave amplitudes that are nearly equal to the mean water depth linear wave theory showed very good agreement with data measurements across the reef illustrate the importance of including both wave transport owing tostokes drift as well as the eulerianmean transportwhen computing the fluxes over the reef finally the observed setup closely follows the theoretical relationship derived from classic radiation stress theory although the two parameters that appear in the model one reflecting wave breaking the other the effective depth over the reef crest must be chosen to match theory to data

numerical modeling of low frequency wave dynamics over a fringing coral reef abstract low frequency infragravity wave dynamics on a fringing coral reef were investigated using the numerical model xbeach roelvink et al 2009 first the skill of the model was evaluated in one and two dimensions based on its predictions of short waves 0 04 0 2 hz infragravity waves 0 004 0 04 hz and water level measurements tidal and wave setup obtained during a 2009 field study at ningaloo reef in western australia the model calibration was sensitive to friction coefficients for short waves and current infragravity bed friction which were assumed independent in this model study although the one dimensional cross shore model captured the gradients in the dominant hydrodynamic processes at the site a high current ig bed friction coefficient was required this resulted in an overestimation and a phase lag between the observed and predicted wave setup signal in the two dimensional model a lower more realistic current infragravity wave friction coefficient was required to achieve optimum performance due to the presence of significant reef and lagoon mean flows in the model which led to reduced setup across the reef the infragravity waves were found to propagate from the surf zone across the reef in a dominantly cross shore direction towards the shore but with substantial frictional damping the infragravity waves were strongly modulated also over the reef by tidal depth variations primarily due to the variability in frictional dissipation rates when the total water depth over the reef varied two mean wave driven circulation cells were observed in the study area with cross shore flow becoming more alongshore dominated before exiting the system via the two channels in the reef the results reveal that short waves dominated bottom stresses on the forereef and near the reef crest however inside the lagoon infragravity waves become increasingly dominant accounting up to 50 of the combined bottom stresses

pollen and charcoal based evidence for climatic and human impact on vegetation in the northern edge of wuyi mountains china during the last 8200 years pollen and charcoal records derived from the sediment core of lantianyan lty peat bog northern wuyi mountain chains eastern subtropical china provide valuable information of landscape evolutio

forcing of resonant modes on a fringing reef during tropical storm man yi 1 open basin resonant modes have been observed at tidal frequencies on coastal shelves but their excitation on coral reef platforms has only been suggested the topography of and water depth over most fringing reefs correspond to resonant periods that are the order of tens of minutes and fall outside of the energetic part of the wave spectrum during tropical storm man yi low frequency near resonant oscillations dominated the variance of the sea surface elevation at the shoreline of ipan reef guam the excitation of the resonant modes resulted both from a large increase in water level over the reef due to wave setup which increased the resonant frequencies and the occurrence of wave group forcing with time scales commensurate with these increased resonant frequencies

3500 year western pacific storm record warns of additional storm activity in a warming warm pool abstract frequent storm surges often cause catastrophic impacts on human lives and the global economy however these phenomena are not well understood in this study a regional storm reconstruction is performed based on a grain size analysis and stratigraphic modelling of the accelerator mass spectrometry radiocarbon dates of benthic foraminifera from two neighbouring lagoon cores from lingyang reef in the xisha islands located in the northern south china sea of the western pacific the dating results from the lagoon cores reveal a 3500 year depositional history three different depositional units are recognized based on a time series of distinct grain size variations that correspond to the following three stages of storm activity intense and frequent storms from 3500 to 3100 cal yr bp and 1800 cal yr bp to present and weak and infrequent storms from 3100 to 1800 cal yr bp a high sedimentation rate remarked by reverse and chaos age is observed from 2800 to 2600 cal yr bp in both cores and it was likely associated with a tsunami event in addition grain size variability may be associated with changes over time caused by the synchronous asian monsoon and may also be correlated with climate records retrieved from the ice cores from greenland thus this variability could indicate pervasive global climatic teleconnections the overall temporal patterns of the isolated coral branches and shells from the sediment sequences are well correlated with the high sea surface temperatures in the western tropical pacific we suggest that increasing sea surface temperatures in the future may lead to more intense storm activity in the western pacific warm pool as the planet warms

observations of wave transformation over a fringing coral reef and the importance of low frequency waves and offshore water levels to runup overwash and coastal flooding many low lying tropical islands are susceptible to sea level rise and often subjected to overwash and flooding during large wave events to quantify wave dynamics and wave driven water levels on fringing coral reefs a 5 month deployment of wave gauges and a current meter was conducted across two shore normal transects on roi namur island in the republic of the marshall islands these observations captured two large wave events that had waves with maximum heights greater than 6 m with peak periods of 16 s over the fore reef the larger event coincided with a peak spring tide leading to energetic highly skewed infragravity 0 04 0 004 hz and very low frequency 0 004 0 001 hz waves at the shoreline which reached heights of 1 0 and 0 7 m respectively water surface elevations combined with wave runup reached 3 7 m above the reef bed at the innermost reef flat adjacent to the toe of the beach resulting in flooding of inland areas this overwash occurred during a 3 h time window that coincided with high tide and maximum low frequency reef flat wave heights the relatively low relief characteristics of this narrow reef flat may further drive shoreline amplification of low frequency waves due to resonance modes these results 1 demonstrate how the coupling of high offshore water levels with low frequency reef flat wave energetics can lead to large impacts along fringing reef lined shorelines such as island overwash and 2 lend support to the hypothesis that predicted higher sea levels will lead to more frequent occurrences of these extreme events negatively impacting coastal resources and infrastructure

pollen and non pollen palynomorph analyses of upper holocene sediments from dianshan yangtze coastal lowlands china hydrology vegetation history and human activity abstract the coastal deltaic plain of the yangtze river between taihu lake tai and shanghai in eastern china has been the scene of human settlement and agriculture since the early neolithic becoming increasingly intensive in the upper holocene when delta accretion and the establishment of a stable hydrological regime of freshwater lakes and wetlands allowed the development of extensive agriculture and complex society in late prehistoric and dynastic times during this period the area was significantly affected by changes in sea level climate and vegetation resulting in a dynamic and complex environmental history however little research has concentrated on environmental change and human impacts during the last few millennia this study focuses on this late period presenting the results of integrated sedimentary microfossil and radiocarbon analyses from a core near the eastern margin of lake dianshan to the east of taihu after the withdrawal of intertidal conditions and the conversion to freshwater lake at the core site about 2600 cal yr bp pollen and algal spore data show that increased sedimentation gradually reduced freshwater depth until a surface peat formed ca 1500 cal yr bp this also dates the start of a switch in woodlands from sub tropical and warm temperate trees to a mainly cool temperate and coniferous tree flora under climatic cooling and human impact after this time water depths at the site increased greatly partly due to climate change and flooding but also because of the establishment of deepwater paddy agriculture microcharcoal and pollen data show that a major episode of human impact using fire with deforestation and rice cultivation occurred between ca 1500 and 1200 cal yr bp these dates suggest it is one of the latest examples of flooded field paddy cultivation before more intensive agricultural techniques were adopted in the area after ca 800 cal yr bp

the importance of explicitly modelling sea swell waves for runup on reef lined coasts abstract the importance of explicitly modelling sea swell waves for runup was examined using a 2d xbeach short wave averaged surfbeat xb sb and a wave resolving non hydrostatic xb nh model of roi namur island on kwajalein atoll in the republic of marshall islands field observations on water levels wave heights and wave runup were used to drive and evaluate both models which were subsequently used to determine the effect of sea level rise and extreme wave conditions on wave runup and its components results show that specifically modelling the sea swell component using xb nh provides a better approximation of the observed runup than xb sb which only models the time variation of the sea swell wave height despite good model performance of both models on reef flat water levels and wave heights xb sb has a bias of 0 108 0 057 m and scatter index of 0 083 0 639 whereas xb nh has bias of 0 132 0 055 m and 0 122 0 490 respectively however both models under predict runup peaks the difference between xb sb and xb nh increases for more extreme wave events and higher sea levels as xb nh resolves individual waves and therefore captures ss wave motions in runup however for even larger forcing conditions with offshore wave heights of 6 m the island is flooded in both xb sb and xb nh computations regardless the sea swell wave energy contribution in such cases xb sb would be adequate to model flooding depths and extents on the island while requiring 4 5 times less computational effort

the dynamics of infragravity wave transformation over a fringing reef a 3 week field study was conducted to investigate the dynamics of low frequency infragravity wave motions over a fringing reef at ningaloo reef western australia short period wave motions 0 04 0 2 hz were observed to dissipate on the reef crest beyond which infragravity wave motions 0 004 0 04 hz gradually dominated toward the lagoon however both the short waves and the infragravity waves were relatively small both 0 3 m on the reef flat owing to the shallow water depth 2 m the results revealed that the surf zone generation of free infragravity wave motions on the steep 1 20 fore reef slope was dominated by breakpoint forcing as opposed to shoaling bound waves which was also supported by detailed numerical simulations of the generation process this is consistent with theory suggesting the efficiency of the breakpoint forcing mechanism should be high in this steep slope regime shoreward propagating infragravity waves traveled across the reef but were damped by bottom friction dissipation however this was at a rate much smaller than experienced by the residual short waves with these rates of frictional dissipation also strongly dependent on the water depth over the reef the infragravity wave heights increased at higher water levels and hence were strongly modulated by the tide due to the strong dissipation of infragravity waves over this wide and shallow reef that is hydraulically rough any seaward propagating infragravity waves that reflected at the shoreline were small leading to the dominance of progressive shoreward propagating infragravity wave motions throughout the reef and lagoon

improving predictions of swash dynamics in xbeach the role of groupiness and incident band runup abstract in predicting storm impacts on sandy coasts possibly with structures accurate runup and overtopping simulation is an important aspect recent investigations stockdon et al 2014 palmsten and splinter 2016 show that despite accurate predictions of the morphodynamics of dissipative sandy beaches the xbeach model roelvink et al 2009 does not correctly simulate the individual contributions of set up and infragravity and incident band swash to the wave run up in this paper we describe an improved numerical scheme and a different way of simulating the propagation of directionally spread short wave groups in xbeach to better predict the groupiness of the short waves and the resulting infragravity waves the new approach is tested against field measurements from the delilah campaign at duck nc and against video derived runup measurements at praia de faro a relatively steep sandy beach compared to the empirical fit by vousdoukas et al 2012 the xbeach model performs much better for more extreme wave conditions which are severely underestimated by existing empirical formulations for relatively steep beaches incident band swash cannot be neglected and a wave resolving simulation mode is required therefore in this paper we also test the non hydrostatic wave resolving model within xbeach for runup and overtopping against three datasets results for a high quality flume test show non hydrostatic xbeach predicts the run up height with good accuracy maximum deviation 15 a case with a very shallow foreshore typical for the belgian coast at wenduine was compared against detailed measurements overall the model shows correct behavior for this case finally the model is tested against a large number 551 of physical model tests of overtopping from the clash database for relatively high overtopping discharges the non hydrostatic xbeach performs quite well with increasing accuracy for increasing overtopping rates however for relatively low overtopping rates of less than 10 20 l m s the model systematically underestimates measured overtopping rates

modelling storm impacts on beaches dunes and barrier islands a new nearshore numerical model approach to assess the natural coastal response during time varying storm and hurricane conditions including dune erosion overwash and breaching is validated with a series of analytical laboratory and field test cases innovations include a non stationary wave driver with directional spreading to account for wave group generated surf and swash motions and an avalanching mechanism providing a smooth and robust solution for slumping of sand during dune erosion the model performs well in different situations including dune erosion overwash and breaching with specific emphasis on swash dynamics avalanching and 2dh effects these situations are all modelled using a standard set of parameter settings the results show the importance of infragravity waves in extending the reach of the resolved processes to the dune front the simple approach to account for slumping of the dune face by avalanching makes the model easily applicable in two dimensions and applying the same settings good results are obtained both for dune erosion and breaching

holocene vegetation dynamics in response to climate change and human activities derived from pollen and charcoal records from southeastern china abstract our knowledge about the holocene evolution of the east asian summer monsoon easm and its relation to human activities remains incomplete a detailed palynological investigation of two sediment sections from the daiyun mountain nature reserve ca 25 38 25 44 n 118 05 118 21 e fujian province suggests easm controlled subtropical climate conditions that were wetter and warmer than present over the early and middle holocene after 5700 cal yr bp steadily increasing non arboreal pollen and fern spore percentages imply an attenuation of the easm the general climate trend is interrupted by several century scale changes in composition and concentration of arboreal pollen taxa around 8200 7200 6300 and 4400 cal yr bp coinciding with weaker precipitation and lower temperature as suggested by the easm oxygen isotope record our results further support the hypothesis that the natural vegetation cover of southern china was not markedly affected by human activities until 3000 cal yr bp the pollen records suggest a quick decrease in the forest cover ca 3000 2450 cal yr bp followed by a generally open agricultural landscape and spread of secondary pine forests this pattern is in line with a major population growth promoted by the southward expansion of rice based agriculture across the region that postdates the widely accepted holocene climate optimum by several millennia this highlights the multidimensional significance of this term which is commonly used in palaeoenvironmental and archaeological studies and should be consequently applied with respect to the specific issue under consideration

the influence of coral reefs and climate change on wave driven flooding of tropical coastlines a numerical model xbeach calibrated and validated on field data collected at roi namur island on kwajalein atoll in the republic of marshall islands was used to examine the effects of different coral reef characteristics on potential coastal hazards caused by wave driven flooding and how these effects may be altered by projected climate change the results presented herein suggest that coasts fronted by relatively narrow reefs with steep fore reef slopes 1 10 and steeper and deeper smoother reef flats are expected to experience the highest wave runup wave runup increases for higher water levels sea level rise higher waves and lower bed roughness coral degradation which are all expected effects of climate change rising sea levels and climate change will therefore have a significant negative impact on the ability of coral reefs to mitigate the effects of coastal hazards in the future

deformation and recrystallization of plagioclase along a temperature gradient an example from the bergell tonalite abstract syn to post mylonitic tilting of the bergell tonalite allows investigation of the deformation and recrystallization of plagioclase grains along a temperature gradient from the lower to the upper amphibolite facies at the lowest temperatures recrystallization occurs by nucleation and growth of new grains having a different composition from the old grains in contrast at the highest temperatures recrystallization occurs by subgrain rotation associated with grain boundary migration the temperature increase is inferred to induce this transition in two ways first at higher temperatures the anorthite content of the new grains is higher and thus the comositional difference between old and new grains is lower hence the chemical driving potential is small compared with recrystallization at lower temperatures second higher temperatures facilitate climb of dislocations and thus subgrain formation as well as grain boundary mobility the temperature increase is also associated with a transition in the dominant deformation mechanism intracrystalline plasticity dominates deformation at lower temperatures whereas at higher temperatures deformation occurs primarily by diffusion accommodated grain boundary sliding as indicated by the weakening of the indicatrix preferred orientation and the formation of a mixed plagioclase biotite matrix with increasing deformation therefore the strength of the mid to lower crust may be overestimated by dislocation creep flow laws for plagioclase lower crust rheology for polyphase rocks is better approximated by constitutive relationships involving diffusion accommodated grain boundary sliding

textural and mechanical evolution with progressive strain in experimentally deformed aplite determining meaningful flow laws for the polyphase aggregates that characterize the crust is difficult because the strength of such aggregates depends on the strengths volume proportions and geometrical arrangement of their constituent phases and all of those factors may change with progressive strain in order to investigate some of these factors we have performed a series of axial compression experiments on a fine grained granite aplite over a range of shortening strains 20 85 and temperatures 700 900 c at 1 5 10 6 s 1 and 1400 mpa we have also done comparison experiments on pure quartz and feldspar aggregates the aplite is composed of 1 3 quartz and 2 3 oligoclase and microcline with minor biotite and magnetite the quartz grains are dispersed in a continuous matrix of feldspar optical and tem scale microstructures indicate that the deformation mechanisms of the quartz and feldspar grains in the aplites are similar to those of pure quartz and feldspar aggregates deformed at the same conditions the feldspars deform by semi brittle flow at 700 and 800 c and by recrystallization accommodated dislocation creep at 900 c while quartz deforms by recrystallization accommodated dislocation creep at 700 c and by climb accommodated dislocation creep at 800 and 900 c pure albite aggregates are stronger than quartz aggregates over this range of conditions however in the aplite an apparent strength reversal is inferred from grain strain measurements and changes in phase distribution with increasing temperature at 700 c the dispersed quartz grains in the aplite remain less deformed than the feldspar grains because the scarcity of quartz quartz grain boundaries limits recovery by grain boundary migration recrystallization causing the quartz strength to rise above that of feldspar however the aplite is weaker than a pure feldspar aggregate because cracking is enhanced by stress concentrations at the quartz grains at 800 c the two phases undergo approximately equal strain because easy dislocation climb in quartz allows individual grains to strain homogeneously the aplite strength is close to that of a pure feldspar aggregate at 900 c the initially continuous feldspar grains deform inhomogeneously and undergo microboudinage while the quartz grains deform homogeneously and gradually become more interconnected and undergo higher strain than the feldspars the aplite strength is initially closer to that of a feldspar aggregate but with increasing strain it becomes closer to that of a quartz aggregate the aplite undergoes strain softening over the whole range of conditions at 700 and 800 c the weakening is due to grain boundary migration recrystallization of feldspar in the fine grained crush products along grain scale faults at 900 c the weakening is due to a combination of grain boundary migration recrystallization of the feldspars plus increasing interconnection of the weaker quartz grains these results demonstrate that the textural evolution of a polyphase aggregate with increasing strain is determined by both the phase distribution and the deformation mechanism of each phase and that very high strains may be required to approach microstructural and mechanical steady state therefore measuring or calculating a flow law appropriate for granite at mid crustal conditions is not simple

numerical modeling of infragravity wave response during delilah 1 the nearshore circulation model shorecirc is applied to simulate the infragravity wave conditions at two intervals during the 1990 delilah campaign at duck n c the model has been extended to solve the energy equation for random short waves on the timescale of the wave groups which acts as a wave driver for the long wave model to simulate the wave conditions an algorithm has been derived which synthesizes a directional offshore wavefield from measured data including the bound directional low frequency components the model data comparison shows that the mean short wave transformation and mean longshore current are predicted well the structure of the infragravity spectrum as measured in the nearshore array is correctly represented albeit that the energy levels are underpredicted in most locations the 2 d frequency longshore wavenumber spectra show that the infragravity wave energy consists mostly of edge waves and that the computations qualitatively resemble the measurements it is shown that for 1 day bar trapped edge waves are present the model is also used to show that the influence of the longshore variability is small for this particular beach and that the directional spreading in the offshore wave field is critical in predicting the nearshore infragravity wave conditions correctly edge waves which propagate against the current are generated by the directionally broad short wave forcing and to a lesser extent by back scattering the nonlinear terms are relatively unimportant for the prediction of the infragravity wave climate the cross shore gradient of the onshore directed radiation stress is the most important of the forcing terms

magnetic susceptibility evidence of monsoon variation on the loess plateau of central china during the last 130 000 years the magnetic susceptibility of loess and paleosols in central china represents a proxy climate index closely related to past changes of precipitation and vegetation and thus to summer monsoon intensity time series of magnetic susceptibility constructed for three loess paleosol sequences in the southern part of the chinese loess plateau document the history of summer monsoon variation during the last 130 000 yr they correlate closely with the oxygen isotope record of stages 1 to 5 in deep sea sediments soils were forming during intervals of strong summer monsoon whereas loess units were deposited at times of reduced monsoon intensity the chinese loess paleosol sequence can thus be viewed as a proxy record of asian monsoon variability extending over the last 2 5 myr

spectral wave dissipation over a barrier reef 1 a 2 week field experiment was conducted to measure surface wave dissipation on a barrier reef at kaneohe bay oahu hawaii wave heights and velocities were measured at several locations on the fore reef and the reef flat which were used to estimate rates of dissipation by wave breaking and bottom friction dissipation on the reef flat was found to be dominated by friction at rates that are significantly larger than those typically observed at sandy beach sites this is attributed to the rough surface generated by the reef organisms which makes the reef highly efficient at dissipating energy by bottom friction results were compared to a spectral wave friction model which showed that the variation in frictional dissipation among the different frequency components could be described using a single hydraulic roughness length scale surveys of the bottom roughness conducted on the reef flat showed that this hydraulic roughness length was comparable to the physical roughness measured at this site on the fore reef dissipation was due to the combined effect of frictional dissipation and wave breaking however in this region the magnitude of dissipation by bottom friction was comparable to wave breaking despite the existence of a well defined surf zone there under typical wave conditions the bulk of the total wave energy incident on kaneohe bay is dissipated by bottom friction not wave breaking as is often assumed for sandy beach sites and other coral reefs

nonhydrostatic and surfbeat model predictions of extreme wave run up in fringing reef environments abstract the accurate prediction of extreme wave run up is important for effective coastal engineering design and coastal hazard management while run up processes on open sandy coasts have been reasonably well studied very few studies have focused on understanding and predicting wave run up at coral reef fronted coastlines this paper applies the short wave resolving nonhydrostatic xb nh and short wave averaged surfbeat xb sb modes of the xbeach numerical model to validate run up using data from two 1d alongshore uniform fringing reef profiles without roughness elements with two objectives i to provide insight into the physical processes governing run up in such environments and ii to evaluate the performance of both modes in accurately predicting run up over a wide range of conditions xbeach was calibrated by optimizing the maximum wave steepness parameter maxbrsteep in xb nh and the dissipation coefficient alpha in xb sb using the first dataset and then applied to the second dataset for validation xb nh and xb sb predictions of extreme wave run up rmax and r2 and its components infragravity and sea swell band swash sig and sss and shoreline setup were compared to observations xb nh more accurately simulated wave transformation but under predicted shoreline setup due to its exclusion of parameterized wave roller dynamics xb sb under predicted sea swell band swash but overestimated shoreline setup due to an over prediction of wave heights on the reef flat run up swash spectra were dominated by infragravity motions allowing the short wave but not wave group averaged model xb sb to perform comparably well to its more complete short wave resolving xb nh counterpart despite their respective limitations both modes were able to accurately predict rmax and r2

modelling storm hydrodynamics on gravel beaches with xbeach g abstract in this paper we present a process based numerical model for the prediction of storm hydrodynamics and hydrology on gravel beaches the model comprises an extension of an existing open source storm impact model for sandy coasts xbeach through the application of 1 a non hydrostatic pressure correction term that allows wave by wave modelling of the surface elevation and depth averaged flow and 2 a groundwater model that allows infiltration and exfiltration through the permeable gravel bed to be simulated and is referred to as xbeach g although the model contains validated sediment transport relations for sandy environments transport relations for gravel in the model are currently under development and unvalidated consequently all simulations in this paper are carried out without morphodynamic feedback modelled hydrodynamics are validated using data collected during a large scale physical model experiment and detailed in situ field data collected at loe bar cornwall uk as well as remote sensed data collected at four gravel beach locations along the uk coast during the 2012 2013 storm season validation results show that the model has good skill in predicting wave transformation overall sci 0 14 0 21 run up levels sci

identification and classification of very low frequency waves on a coral reef flat very low frequency vlf 0 001 0 005 hz waves are important drivers of flooding of low lying coral reef islands in particular vlf wave resonance is known to drive large wave runup and subsequent overwash using a five month dataset of water levels and waves collected along a cross reef transect on roi namur island in the republic of the marshall islands the observed vlf motions were categorized into four different classes 1 resonant 2 non resonant standing 3 progressive growing and 4 progressive dissipative waves each vlf class is set by the reef flat water depth and in the case of resonance the incident band offshore wave period using an improved method to identify vlf wave resonance we find that vlf wave resonance caused prolonged 0 5 6 0 hr large amplitude water surface oscillations at the inner reef flat ranging in wave height from 0 14 to 0 83 m it was induced by relatively long period grouped incident band waves and occurred under both storm and non storm conditions moreover observed resonant vlf waves had non linear bore like wave shapes which likely have a larger impact on the shoreline than regular sinusoidal waveforms as an alternative technique to the commonly used fast fourier transformation we propose the hilbert huang transformation that is more computationally expensive but can capture the wave shape more accurately this research demonstrates that understanding vlf waves on reef flats is important for evaluating coastal flooding hazards this article is protected by copyright all rights reserved

influence of the intertropical convergence zone on the east asian monsoon a palaeoclimate record spanning the past 16 000 years with nearly annual time resolution has been obtained from lake huguang maar in china the magnetic properties and titanium content of the lake sediments are thought to reflect changes in the east asian winter monsoon strength thus providing a complement to palaeoclimate archives that record the strength of the rain bearing summer monsoon the records point to an anti correlation between winter and summer monsoon strength best explained by migration of the intertropical convergence zone itcz a belt of low pressure air at the equator interestingly the decline of china s tang dynasty and the mayan civilization broadly coincide with drought periods recorded in lake huguang maar and cariaco basin sediments respectively did major shifts in the position of the itcz catalyse simultaneous events in civilizations on opposite sides of the pacific ocean the asian australian monsoon is an important component of the earth s climate system that influences the societal and economic activity of roughly half the world s population the past strength of the rain bearing east asian summer monsoon can be reconstructed with archives such as cave deposits1 2 3 but the winter monsoon has no such signature in the hydrological cycle and has thus proved difficult to reconstruct here we present high resolution records of the magnetic properties and the titanium content of the sediments of lake huguang maar in coastal southeast china over the past 16 000 years which we use as proxies for the strength of the winter monsoon winds we find evidence for stronger winter monsoon winds before the bolling allerod warming during the younger dryas episode and during the middle and late holocene when cave stalagmites suggest weaker summer monsoons1 2 3 we conclude that this anticorrelation is best explained by migrations in the intertropical convergence zone similar migrations of the intertropical convergence zone have been observed in central america for the period ad 700 to 900 refs 4 6 suggesting global climatic changes at that time from the coincidence in timing we suggest that these migrations in the tropical rain belt could have contributed to the declines of both the tang dynasty in china and the classic maya in central america

holocene vegetation environment and anthropogenic influence in the fuzhou basin southeast china a 40 m sediment core fz4 was collected from the fuzhou basin near the lower reaches of the min river in fujian province on the southeast coast of china the sediment and pollen record contributes to our understanding of holocene paleogeography including local changes in vegetation and climate in the context of neolithic cultural developments the sediment record reveals a fluvial environment in the fuzhou basin during the late pleistocene and it demonstrates that a change from fluvial to estuarine conditions at 9000 cal yr bp resulted from postglacial sea level rise evidence of abundant marine diatoms and tidal flat laminations observed in the fz4 sediments implies that the fuzhou basin was under marine influence between 9000 and 2000 cal yr bp after 2000 cal yr bp a rapid retreat in coastline associated with fluvial aggradation and coastal progradation produced more shallow water for wetlands and initiated formation of the floodplain landscape the pollen record reveals the presence of a dense subtropical forest between ca 9000 and 7000 cal yr bp representing the holocene thermal maximum which is linked with rising sea level and marine transgression in the fuzhou basin between ca 5500 and 2000 cal yr bp the thermophilous forest dominated by castanopsis retreated and coniferous forest expanded reflecting moderate climatic cooling during this period timing of the high frequencies for pinus and ferns correspond with the mid late holocene cooling trend recorded in local mountain peatland and coastal regions of the lower yangtze and hanjiang deltas anthropogenically induced land cover change was negligible prior to the tanshishan cultural period which marks the beginning of neolithic era sedentary village life on the fujian coast around 5500 bp the pollen transition at ca 3000 1500 cal yr bp distinguished by rising frequencies of poaceae and taxa including cyperaceae and artemisia closely associated with agricultural land cover indicates exploitation of newly formed lowlands in the emerging min river floodplain the historic era intensification of rice agriculture is reflected in this trend of rising frequencies of poaceae after ca 2000 cal yr bp we observe the onset of a marine regression followed by evidence for an intensely human impacted environment characterized by sharp rises in pioneer plants such as poaceae and dicranopteris this transition coincides with a rapid retreat of coastline and emergence of the fuzhou basin floodplain

combined infragravity wave and sea swell runup over fringing reefs by super typhoon haiyan super typhoon haiyan struck the philippines on 8 november 2013 marking one of the strongest typhoons at landfall in recorded history extreme storm waves attacked the pacific coast of eastern samar where the violent typhoon first made landfall our field survey confirmed that storm overwash heights of 6 14 m above mean sea level were distributed along the southeastern coast and extensive inundation occurred in some coastal villages in spite of natural protection by wide fringing reefs a wave model based on boussinesq type equations is constructed to simulate wave transformation over shallow fringing reefs and validated against existing laboratory data wave propagation and runup on the eastern samar coast are then reproduced using offshore boundary conditions based on a wave hindcast the model results suggest that extreme waves on the shore are characterized as a superposition of the infragravity wave and sea swell components the balance of the two components is strongly affected by the reef width and beach slope through wave breaking frictional dissipation reef flat resonances and resonant runup amplification therefore flood characteristics significantly differ from site to site due to a large variation of the two topographic parameters on the hilly coast strong coupling of infragravity waves and sea swells produces extreme runup on steep beaches fronted by narrow reefs whereas the infragravity waves become dominant over wide reefs and they evolve into bores on steep beaches

effect of wave frequency and directional spread on shoreline runup 1 wave breaking across the surf zone elevates the mean water level at the shoreline setup and drives fluctuations about the mean runup runup often is divided into sea swell 0 04 0 3 hz and lower frequency infragravity 0 00 0 04 hz components with energetic incident waves runup is dominated by infragravity frequencies and total water levels combined setup and runup can exceed 3 m significantly contributing to coastal flooding and erosion setup and runup observations on sandy beaches are scattered about empirical parameterizations based on near shoreline beach slope and deep water wave height and wavelength accurate parameterizations are needed to determine flooding and erosion risk to coastal ecosystems and communities here numerical simulations with the boussinesq wave model funwavec are shown to statistically reproduce typical empirical setup and runup parameterizations furthermore the model infragravity runuprs ig strongly depends on the incident wave directional and frequency spread about the mean direction and peak frequency realistic directional spread variations change rs ig equivalent to a factor of two variation in incident wave height the modeled rs ig is shown to vary systematically with a new non dimensional spreading parameter that involves peak frequency frequency spread and directional spread this suggests a new parameterization forrs ig potentially useful to predict coastal flooding and erosion

modeling the effect of wave vegetation interaction on wave setup aquatic vegetation in the coastal zone attenuates wave energy and reduces the risk of coastal hazards e g flooding besides the attenuation of sea swell waves vegetation may also affect infragravity band ig waves and wave setup to date knowledge on the effect of vegetation on ig waves and wave setup is lacking while they are potentially important parameters for coastal risk assessment in this study the storm impact model xbeach is extended with formulations for attenuation of sea swell and ig waves and wave setup effects in two modes the sea swell wave phase resolving nonhydrostatic and the phase averaged surfbeat mode in surfbeat mode a wave shape model is implemented to capture the effect of nonlinear wave vegetation interaction processes on wave setup both modeling modes are verified using data from two flume experiments with mimic vegetation and show good skill in computing the sea swell and ig wave transformation and wave setup in surfbeat mode the wave setup prediction greatly improves when using the wave shape model while in nonhydrostatic mode nonlinear intrawave effects are directly accounted for subsequently the model is used for a range of coastal geomorphological configurations by varying bed slope and vegetation extent the results indicate that the effect of wave vegetation interaction on wave setup may be relevant for a range of typical coastal geomorphological configurations e g relatively steep to gentle slope coasts fronted by vegetation

a last glacial and deglacial pollen record from the northern south china sea new insight into coastal shelf paleoenvironment this study presents a marine palynological record of the asian summer monsoon and sea level change in the last glacial maximum lgm and the deglacial period in the northern south china sea scs a fossil core std 235 855 cm in length and 273 surface sediment samples from the northern scs were pollen analysed to reconstruct the paleoenvironment of the continental shelf during the last glacial period results from fossil pollen show that the main pollen source region fundamentally changed from the lgm to the deglacial period as sea level rapidly rose the modern marine surface samples show that pollen concentrations in the estuary of the pearl river are extremely high and modern pollen assemblages are in good agreement with the regional vegetation however wind transport becomes more important in the deeper ocean as the percentages of pinus a taxon with very high pollen production and dispersal capacity is highest in these sediments which otherwise have very low pollen concentrations the concentration of total pollen between surface and fossil pollen samples is compared in order to determine the possible vegetation sources areas for the marine core pollen concentration as high as 100 grains g at the lgm suggested that the paleo shoreline was located within 80 km of the core consequently pollen would mostly have derived from the exposed continental shelf in the northern scs by contrast pollen concentrations were very low due to a much greater transport distance 318 km at present core std 235 under higher sea levels and windblown pollen played a more important role because of the limitation of riverine input into the deep ocean during this highstand period such alternation of pollen flux and source distance should be repeated during all glacial interglacial cycles reflecting closely sea level and climate dynamics according to fossil pollen assemblages from core std 235 we conclude that wetland and or grassland communities with sparse subtropical trees dominated most of the exposed shelf during the lgm rather than forest that characterizes the region today the existence of a predominantly open landscape on the exposed continental shelf suggests lower precipitation during the lgm which in turn indicates a weaker asian summer monsoon this finding is supported by other records from the okinawa trough and the east china sea suggesting that a weaker summer monsoon was a key characteristic of the lgm in east asia

phase boundary mobility in naturally deformed high grade quartzofeldspathic rocks evidence for diffusional creep abstract grain shape fabrics and optical microstructures of some quartzofeldspathic rocks deformed under upper amphibolite facies conditions in the southwestern grenville province ontario canada suggest that quartz and feldspar have accommodated intracrystalline plastic strains by both diffusional and dislocation creep in these rocks quartz and feldspar form polycrystalline domains separated by gently curved and locally cuspate phase boundaries whose morphology is similar in certain respects to the phase boundary morphology of rocks annealed experimentally under hydrostatic stress conditions in the naturally deformed rocks however phase boundary cusps consistently point along the foliation and parallel to the mineral fibre lineation i e in directions of inferred finite extension which implies that phase boundary motion and cusp formation occurred during deformation optical microstructures in feldspar and crystallographic preferred orientations in quartz are consistent with the accommodation of some intracrystalline plastic strains by dislocation creep however the morphology of quartz feldspar phase boundaries cannot be explained by either dislocation creep or static annealing alone we propose that phase boundary motion resulted from a diffusion assisted process involving dissolution at foliation parallel quartz feldspar phase boundaries mass transfer over length scales of the order of feldspar domain size 200 m or greater and precipitation at quartz feldspar phase boundary cusps this study extends the range of natural deformation conditions under which diffusional creep has been identified in quartzofeldspathic rocks it also has important implications for the natural rheological behavior of the mid and lower continental crust

texture and elastic anisotropy of a mylonitic anorthosite from the morin shear zone quebec canada a sample of anorthosite from the granulite facies morin shear zone quebec canada was investigated for crystal preferred orientation and elastic anisotropy time of flight neutron diffraction data obtained with the hippo diffractometer at lansce were analyzed with the rietveld method to obtain orientation distribution functions of the principal phases plagioclase clinopyroxene and orthopyroxene texture and microstructures are compatible with the plastic deformation of the aggregate under high t conditions all mineral phases depict a significant preferred orientation that could be related to the general top to the north shearing history of the morin shear zone texture patterns suggest that 010 001 in plagioclase and 110 001 in clinopyroxene are likely dominant slip systems using preferred orientation data p and s waves velocities and elastic anisotropy were calculated and compared with previous studies to explore elastic properties of rocks with different pyroxene plagioclase mixtures p wave velocity s wave splitting and anisotropy increase with clinopyroxene content seismic anisotropy is linked to the texture symmetry which can lead to large deviations between actual anisotropy and that measured along cartesian xyz sample directions lineation foliation reference frame this is significant for the prediction and interpretation of seismic data particularly for monoclinic or triclinic texture symmetries

organic matter distribution in the modern sediments of the pearl river estuary we determined biomarker concentrations and distributions for surface sediments from 54 sites in the pearl river estuary china we focus on a suite of four biomarker based indicators for relative terrestrial to marine organic matter om source the branched isoprenoid tetraether bit index the ratio of high low molecular weight n alcohols c26 34 c16 18 c26 34 an analogous ratio for n fatty acids and the c29 steroids c29 steroids brassicasterol ratio all four exhibit the same terrestrial to marine transition seen in previous bulk 13c studies but with an abrupt decrease in the relative terrestrial contribution across the delta front to pro delta transition concentrations of terrestrially derived biomarkers show no systematic decrease across the transition instead the decrease in the proportion of terrestrial om is due to a decrease in the sedimentation rate and associated terrestrial om burial across the delta toe this suggests that diagenetic controls on the fate of terrestrial om such as increased biodegradation where sedimentation rate is low are subordinate to sedimentological processes biomarker derived temperature values are cooler than expected for the lower pearl river catchment suggesting that the dominant component of the terrestrial om is derived from the cooler upland regions of the catchment the dominance of input from more distal terrain with greater topographic relief is evidence for the importance of geomorphological control on terrigenous om transport collectively the results demonstrate the importance of sedimentological processes in the supply deposition and transport of terrestrial om

origin of migmatites by deformation enhanced melt infiltration of orthogneiss a new model based on quantitative microstructural analysis a detailed field study reveals a gradual transition from high grade solid state banded orthogneiss via stromatic migmatite and schlieren migmatite to irregular foliation parallel bodies of nebulitic migmatite within the eastern part of the gfohl unit moldanubian domain bohemian massif the orthogneiss to nebulitic migmatite sequence is characterized by progressive destruction of well equilibrated banded microstructure by crystallization of new interstitial phases kfs pl and qtz along feldspar boundaries and by resorption of relict feldspar and biotite the grain size of all felsic phases decreases continuously whereas the population density of new phases increases the new phases preferentially nucleate along high energy like like boundaries causing the development of a regular distribution of individual phases this evolutionary trend is accompanied by a decrease in grain shape preferred orientation of all felsic phases to explain these data a new petrogenetic model is proposed for the origin of felsic migmatites by melt infiltration from an external source into banded orthogneiss during deformation in this model infiltrating melt passes pervasively along grain boundaries through the whole rock volume and changes completely its macro and microscopic appearance it is suggested that the individual migmatite types represent different degrees of equilibration between the host rock and migrating melt during exhumation the melt topology mimicked by feldspar in banded orthogneiss forms elongate pockets oriented at a high angle to the compositional banding indicating that the melt distribution was controlled by the deformation of the solid framework the microstructure exhibits features compatible with a combination of dislocation creep and grain boundary sliding deformation mechanisms the migmatite microstructures developed by granular flow accompanied by melt enhanced diffusion and or melt flow however an ams study and quartz microfabrics suggest that the amount of melt present did not exceed a critical threshold during the deformation to allow free movements of grains

energy transfer between wind waves and low frequency oscillations on a fringing reef ipan guam field observations from a guam fringing reef are used to examine the cross reef energy exchange between high frequency sea and swell ss and low frequency infragravity ig and far infragravity fig waves energetic ss waves significant wave heights 2 4 m break at the outer reef leading to weak 1 m conditions on the shallow reef flat as ss waves shoal on the reef face before breaking ig and fig energy fluxes both increase through nonlinear energy transfer from the ss waves in contrast through the surf zone the ig energy flux decreases whereas fig flux increases the decrease in ig energy flux through the surf zone is attributed to breaking ss waves working against the incident bound ig wave energy which dominates breakpoint forced ig waves yielding a net flux decrease in contrast fig energy flux increases through the surf zone consistent with breakpoint forcing and the absence of an energetic bound fig component on the reef face ig and fig energy fluxes decay on the shallow reef flat due primarily to frictional dissipation with tidal modulations attributed to nonlinear conversion and friction forcing at fig frequencies may lead to a normal mode response on the reef with comparable incoming and outgoing fig energy fluxes at the outer reef flat depending on water level over the reef flat and the degree of frictional dissipation

global characterization of the holocene thermal maximum we analyze the global variations in the timing and magnitude of the holocene thermal maximum htm and their dependence on various forcings in transient simulations covering the last 9000 years 9 ka performed with a global atmosphere ocean vegetation model in these experiments we consider the influence of variations in orbital parameters and atmospheric greenhouse gases and the early holocene deglaciation of the laurentide ice sheet lis considering the lis deglaciation we quantify separately the impacts of the background melt water fluxes and the changes in topography and surface albedo in the analysis we focus on the intensity of the maximum temperature deviation relative to the preindustrial level its timing in the holocene and the seasonal expression in the model the warmest htm conditions are found at high latitudes in both hemispheres reaching 5 c above the preindustrial level while the smallest htm signal is seen over tropical oceans less than 0 5 c this latitudinal contrast is mostly related to the nature of the orbitally forced insolation forcing which is also largest at high latitudes and further enhanced by the polar amplification the holocene timing of the htm is earliest before 8 ka bp in regions not affected by the remnant lis particularly nw north america e asia n africa n south america the middle east ne siberia and australia compared to the early holocene insolation maximum the htm was delayed by 2 3 ka over ne north america and regions directly downwind from the lis a similar delay is simulated over the southern ocean while an intermediate lag of about 1 ka is found over most other continents and oceans the seasonal timing of the htm over continents generally occurs in the same month as the maximum insolation anomaly whereas over oceans the htm is delayed by 2 3 months exceptions are the oceans covered by sea ice and north africa were additional feedbacks results in a different seasonal timing the simulated timing and magnitude of the htm are generally consistent with global proxy evidence with some notable exceptions in the mediterranean region sw north america and eastern eurasia 2012 elsevier ltd

wave transformation and shoreline water level on funafuti atoll tuvalu the influence of sea swell ss waves infragravity ig waves and wave setup on maximum runup rmax is investigated across different tidal stages on fatato island funafuti atoll tuvalu field results illustrate that ss waves are tidally modulated at the shoreline with comparatively greater wave attenuation and setup occurring at low tide versus high tide a shoreward increase in ig wave height is observed across the 100 m wide reef flat at all tidal elevations with no tidal modulation of ig wave height at the reef flat or island shoreline a 1 d shock capturing green naghdi solver is used to replicate the field deployment and analyze rmax model outputs for ss wave height ig wave height and setup at the shoreline match field results with model skill 0 96 model outputs for rmax are used to identify the temporal window when geomorphic activity can occur on the beach face during periods of moderate swell energy waves can impact the beach face at spring low tide due to a combination of wave setup and strong ig wave activity under mean wave conditions the combined influence of setup ig waves and ss waves results in interaction with island sediment at midtide at high tide ss and ig waves directly impact the beach face overall wave activity is present on the beach face for 71 of the study period a significantly longer duration than is calculated using mean water level and topographic data

microstructures in quartz and feldspars of the bomdila gneiss from western arunachal himalaya northeast india implications for the geotectonic evolution of the bomdila mylonitic zone abstract microstructures of the bomdila gneiss bg that intruded the metapelites of the lesser himalayan crystallines lhc in the western arunachal himalaya were studied to understand the deformation mechanisms and temperatures during deformation the lhc is delimited at the base by the bomdila thrust bt and the main central thrust mct at the top the microstructural features of quartz and feldspar in the bg indicate that the rocks underwent an early stage of deep level ductile deformation superimposed by shallow level brittle deformation during a later stage of deformation grain boundary migration and subgrain rotation recrystallization are the main deformation mechanisms for recrystallization of quartz and feldspars pressure solution and solution transfer were also important at the base of the bomdila mylonitic zone both the feldspars plagioclase and k feldspar and quartz show dynamic recrystallization with growth of myrmekite at the upper level while the development of quartz subgrains and fractured in feldspars are dominate at the lower level the deformation microstructures of bg suggest that the bomdila mylonitic zone shows an inverted thermal profile towards the mct i e increase in deformation temperature from 400 c at the lower zone to 500 600 c at the upper zone of the gneiss the microstructural variations and decreasing temperatures of deformation from west to east indicate that the lhc initially buried below higher himalayan crystallines hhc along the mct have been exhumed along the bt shear criteria indicates top to the se displacement in agreement with the kinematics of the lhc along the bt producing of an inverted thermal profile in the study area may be related to imbrication and post metamorphic shearing

water level effects on breaking wave setup for pacific island fringing reefs the effects of water level variations on breaking wave setup over fringing reefs are assessed using field measurements obtained at three study sites in the republic of the marshall islands and the mariana islands in the western tropical pacific ocean at each site reef flat setup varies over the tidal range with weaker setup at high tide and stronger setup at low tide for a given incident wave height the observed water level dependence is interpreted in the context of radiation stress gradients specified by an idealized point break model generalized for nonnormally incident waves the tidally varying setup is due in part to depth limited wave heights on the reef flat as anticipated from previous reef studies but also to tidally dependent breaking on the reef face the tidal dependence of the breaking is interpreted in the context of the point break model in terms of a tidally varying wave height to water depth ratio at breaking implications for predictions of wave driven setup at reef fringed island shorelines are discussed

palaeoclimatic and sedimentary history from magnetic susceptibility of loess in china the magnetostratigraphic age of the oldest loess sediments in the central chinese loess plateau investigated so far has recently been placed at ca 2 4 million years b p thus glaciations in central asia which are believed to provide the detritus for the formation of chinese loess commenced at the same time as the first ice rafted debris sank into the ocean basins of the northern hemisphere shackleton et al 1984 lithologic palaeontologic geochemical and especially rock magnetic variations throughout the loess column are indicative of palaeoclimatic fluctuations during loess deposition the variations of magnetic low field susceptibility in loess closely resemble those of the marine oxygen isotope record shackleton and opdyke 1976 and establish for the first time a continuous record of the pleistocene glacial and interglacial stages in a continental section spectral analysis of the rock magnetic time series indicates slow apparent sedimentation during interglacial periods which are characterized mainly by calcium dissolution and related compaction of the soils variable aeolic sediment influx as well as erosion and or polygenetic soil formation may also strongly influence the sedimentary history

a high resolution absolute dated holocene and deglacial asian monsoon record from dongge cave china abstract we present a continuous record of the asian monsoon over the last 16 ka from 18o measurements of stalagmite calcite over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230th dates 18o and therefore asian monsoon intensity generally follows changes in insolation although changes in 18o are generally accommodated in abrupt shifts in contrast to smoothly varying insolation indicating that threshold effects may be important 18o decreased dramatically 3 at the start of the holocene 11 5 ka and remained low for 6 ka four positive 18o events centered at 11225 97 yr bp 1 05 10880 117 yr bp 1 15 9165 75 yr bp 1 4 and a double event centered at 8260 64 yr bp 1 1 and 8080 74 yr bp 1 0 punctuated this period of high monsoon intensity all four events correlate within error with climate changes in greenland ice cores thus the relationship between the asian monsoon and the north atlantic observed during the glacial period appears to continue into the early holocene in addition three of the four events correlate within error with outburst events from lake agassiz the decline of monsoon intensity in the mid late holocene is characterized by an abrupt positive shift in 18o which occurs at 3550 59 yr bp 1 1 in 100 yr in addition the holocene is punctuated by numerous centennial and multi decadal scale events amplitudes 0 5 to 1 up to half the amplitude of the glacial interstadial events seen in the last glacial period thus holocene centennial and multi decadal scale monsoon variability is significant although not as large as glacial millennial scale variability the monsoon shows a strong connection with northern south american hydrological changes related by changes in itcz position spectral analysis of the 18o record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing however there are numerous other significant peaks including peaks at el nino frequencies observed for high resolution portions of the record between 8110 and 8250 yr which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling holocene monsoon climate in addition for this high resolution portion we observe a distinctive biennial oscillation of the asian monsoon which has been associated with the tropospheric biennial oscillation tbo

vegetation climate and sea level in the past 55 000 years hanjiang delta southeastern china abstract pollen in quaternary deposits from the subtropical hanjiang delta records three major phases in the local vegetation and climate history during the last 55 000 yr 1 a prevalent cool to temperate and humid climate at ca 24 000 14c yr b p is indicated by abundant pollen of temperate trees including conifers 2 between 20 000 and 15 000 14c yr b p a cold dry environment was associated with low sea level during the last glaciation leading to subaerial exposure weathering and interruption of sedimentation as well as departure from the region of dacrydium and sonneratia 3 a short term expansion of grassland at ca 10 300 14c yr b p reduced the predominant lauraceae fagaceae evergreen forest possibly corresponding to the younger dryas cooling the combined data indicate a maximum sea level rise in the mid holocene 7500 4000 14c yr b p and a marine influence in the late pleistocene at 45 000 20 000 14c yr b p the holocene warming however did not bring back moisture sensitive taxa indicating high seasonal aridity probably caused by renewed monsoon conditions

modeling of depth induced wave breaking under finite depth wave growth conditions 1 recent studies have shown that the spectral wind wave model swan simulating waves nearshore underestimates wave heights and periods in situations of finite depth wave growth in this study this inaccuracy is addressed through a rescaling of the battjes and janssen 1978 bore based model for depth induced breaking considering both sloping bed surf zone situations and finite depth wave growth conditions it is found that the variation of the model error with the breaker index bj in this formulation differs significantly between the two types of conditions for surf zones clear optimal values are found for the breaker index by contrast under finite depth wave growth conditions model errors asymptotically decrease with increasing values of the breaker index weaker dissipation under both the surf zone and finite depth wave growth conditions optimal calibration settings of bj were found to correlate with the dimensionless depth kpd where kp is the spectral peak wave number and d is the water depth and the local mean wave steepness subsequently a new breaker index based on the local shallow water nonlinearity expressed in terms of the biphase of the self interactions of the spectral peak is proposed implemented in the bore based breaker model of thornton and guza 1983 this breaker index accurately predicts the large difference in dissipation magnitudes found between surf zone conditions and finite depth growth situations hence the proposed expression yields a significant improvement in model accuracy over the default battjes and janssen 1978 model for finite depth growth situations while retaining good performance for sloping bed surf zones

a continuous record of vegetation and climate change over the past 50 000years in the fujian province of eastern subtropical china abstract a 425 cm core has been collected from the gantang subalpine peat bog in pingnan county fujian province of southern china high resolution pollen analysis of the core has allowed for the reconstruction of past vegetation and climate changes over the last 50 000 years today fujian province is located in the eastern part of middle subtropical zone where the dominant vegetation is evergreen broadleaved forest that receives its precipitation from the east asian monsoon the pollen record testifies that the vegetation in fujian varied between subtropical evergreen and warm temperate deciduous forests during the last glacial interglacial cycle it appears that during marine oxygen isotope stage 3 this area was covered with broadleaved forest suggesting warm and wet subtropical condition whereas the flora was quite different with many ancient elements the last glacial maximum is distinguished by an increase in warm temperate deciduous taxa particularly fagus and alnus accompanied by abundant ericaceae implying a spatial shift of zonal vegetation during this coldest episode in the world local swamp developed soon after the younger dryas event coinciding with the formation of peatlands in the northern hemisphere possibly linked with atmospheric carbon accumulation a rapid increase in evergreen broadleaved taxa that dominated the local forest occurred at ca 8 2 cal ka bp indicating the inception of the regional thermal maximum during the holocene which was generally characterised by more humid conditions the middle to late holocene sees a progressive decline in arboreal elements and an increase in grasses and ericaceae these changes beginning from around 4 ka cal bp were concordant with the general weakening of the east asian monsoon during the holocene corresponding with an orbitally induced reduction of boreal summer insolation this is the first terrestrial high resolution record from eastern part of middle subtropical areas that evaluates the forest changes through the last glacial interglacial cycle

microstructural shear criteria associated with grain boundary sliding during ductile deformation abstract experimental studies on rock analogues are described which establish that certain microstructures diamond grain structures tabular grain structures and asymmetric grain boundary bulges can be used to determine i if deformation was coaxial or non coaxial and ii the sense of shear in zones of non coaxial deformation mechanisms for the development of the structures are described which involve the linked operation of grain boundary sliding and migration

dry or humid mid holocene humidity changes in arid and semi arid china abstract spatial changes of effective moisture during the mid holocene have been reconstructed based on the compilation of recently published paleoclimate records including ice core lake level pollen assemblage and loess paleosol records both geological data and the spatial pattern indicate that it was dry in deserts during the mid holocene but the timing of the beginning and end of dry intervals differs from place to place deserts having higher aridity index values remain dry longer dry intervals during the mid holocene are more possibly asynchronous than synchronous in arid and semi arid china in the xinjiang region except in sites located in deserts the climate is generally wet during 7000 5000 a bp in the northern qinghai tibetan plateau effective moisture in most sites began to decrease after 5000 a bp the climate became dry after 4000 a bp except in the deserts in the loess plateau and the inner mongolia plateau