late holocene sea level changes and isostasy in western denmark abstract cores and exposed cliff sections in salt marshes around ho bugt a tidal embayment in the northernmost part of the danish wadden sea were subjected to 14c dating and litho and biostratigraphical analyses to reconstruct paleoenvironmental changes and to establish a late holocene relative sea level history four stages in the late holocene development of ho bugt can be identified 1 groundwater table rise and growth of basal peat from at least 2300 bc to ad 0 2 salt marsh formation 0 to ad 250 3 a freshening phase ad 250 to ad 1600 culminating in the drying out of the marshes and producing a distinct black horizon followed by an aeolian phase with sand deposition and 4 renewed salt marsh deposition ad 1600 to present from 16 calibrated ams radiocarbon ages on fossil plant fragments and 4 calibrated conventional radiocarbon ages on peat we reconstructed a local relative sea level history that shows a steady sea level rise of 4 m since 4000 cal yr bp contrary to suggestions made in the literature the relative sea level record of ho bugt does not contain a late holocene highstand relative sea level changes at ho bugt are controlled by glacio isostatic subsidence and can be duplicated by a glacial isostatic adjustment model in which no water is added to the world s oceans after ca 5000 cal yr bp

sea level change along the french atlantic and channel coasts since the time of the last glacial maximum abstract holocene sea level change along the french atlantic and english channel coast is not uniform because of the response of the crust to the changing ice and water loads in late pleistocene and holocene time the pattern of the spatial variability is a north south trend of decreasing sea levels levels at any time this results primarily from the isostatic response to the melting of the fennoscandian ice sheet superimposed upon this is a mainly east west trend resulting from the isostatic response of the crust to the addition of the meltwater into the atlantic ocean the combined effect is that at any time sea levels vary spatially along this coastline by amounts that are predicted to reach 20 m from the time of the last glacial maximum to about 10 000 radiocarbon yr ago about 15 m at 8000 yr ago and about 10 m at 6000 yr ago thus observations of past sea levels should not be combined into a single sea level curve unless first corrected for the glacio hydro isostatic factors alternatively the data should only be used to construct regional curves for relatively short sections of the coastline such as pas de calais and picardie normandie cotes du nord finistere or the vendee and charente maritime region even within such constrained regions the spatial variability may still be of the order of a few meters analysis of the observational data by region indicates that major oscillations in sea level are unlikely to have occurred that levels at no location exceeded the present mean sea level and that there may have been a small 3 m increase in eustatic sea level over the past 6000 yr palaeoshorelines and palaeo water depths for the english channel and the atlantic coast shelf have been predicted using the isostatic and eustatic models and the results indicate that in situ marine deposits older than 6000 7000 yr are unlikely to be found along many sections of the present coastline

quantitative constraints on the sea level fall that terminated the littorina sea stage southern scandinavia abstract the island of anholt in the kattegat sea southern scandinavia is made up largely of an extensive beach ridge plain as a result of post glacial uplift the earliest beach ridge and swale deposits are now raised 8 9 m above present mean sea level it appears that growth of the plain has been almost uninterrupted over the past 7500 years here we constrain the evolution of this plain between 6300 and 1300 years ago using optically stimulated luminescence dates the topography and internal architecture of the fossil shoreline deposits were measured on high resolution maps and in ground penetrating radar gpr reflection data with a vertical resolution of 0 25 m shoreline topography shows significant changes with time and it appears that one of the most striking changes took place between 4300 and 3600 years ago in the shoreline deposits corresponding to this time interval the surface drops by around 3 5 m suggesting a marked fall in relative sea level assuming a constant uplift rate of 1 2 mm yr the corresponding drop in absolute sea level is estimated to be around 2 6 m this marked sea level fall in 700 years took place at the transition from the middle holocene thermal maximum to the late holocene thermal decline or at the end of the littorina sea stage in the baltic sea region

optically stimulated luminescence age controls on late pleistocene and holocene coastal lithosomes north carolina usa luminescence ages from a variety of coastal features on the north carolina coastal plain provide age control for shoreline formation and relative sea level position during the late pleistocene a series of paleoshoreline ridges dating to marine isotope stage mis 5a and mis 3 have been defined the kitty hawk beach ridges on the modern outer banks yield ages of 3 to 2 ka oxygen isotope data are used to place these deposits in the context of global climate and sea level change the occurrence of mis 5a and mis 3 shorelines suggests that glacio isostatic adjustment gia of the study area is large ca 22 to 26 m as suggested and modeled by other workers and or mis 3 sea level was briefly higher than suggested by some coral reef studies correcting the shoreline elevations for gia brings their elevation in line with other sea level indicators the age of the kitty hawk beach ridges places the holocene shoreline well west of its present location at ca 3 to 2 ka the age of shoreline progradation is consistent with the ages of other beach ridge complexes in the southeast usa suggesting some regionally contemporaneous forcing mechanism

iceberg scours along the southern u s atlantic margin rapid climate fluctuations associated with ice sheet oscillations have resulted in pulses of iceberg discharge that are recorded by iceberg scour marks along continental shelves and ice rafted debris deposits across the north atlantic iceberg transport is largely controlled by ocean surface currents therefore iceberg trajectories can serve as a proxy for paleo circulation studies records of iceberg transport from ice rafted debris i e heinrich layers in the north atlantic suggest that most icebergs released during quaternary glaciations were entrained in a cyclonic subpolar gyre restricted to polar and mid latitudes however new data suggest that there may have been an additional southerly component of transport along the western atlantic margin here we present evidence of extensive iceberg scouring across the upper slope offshore of south carolina 1000 km south of the proximal ice margin during quaternary glacial maximums the location and orientation of the keel marks suggest that icebergs were entrained in a southwestward flowing coastal current at present warm waters of the rapid northeastward flowing gulf stream bathe the upper slope off the southeastern united states an offshore shift in the gulf stream axis during sea level lowstand may have allowed glacially fed coastal currents to penetrate farther south this may be the first evidence of iceberg rafting to subtropical latitudes in the north atlantic

causes of reduced north atlantic storm activity in a cam3 simulation of the last glacial maximum abstract the aim of this paper is to determine how an atmosphere with enhanced mean state baroclinity can support weaker baroclinic wave activity than an atmosphere with weak mean state baroclinity as a case study a last glacial maximum lgm model simulation previously documented to have reduced baroclinic storm activity relative to the modern day climate simulated by the same model despite having an enhanced midlatitude temperature gradient is considered several candidate mechanisms are evaluated to explain this apparent paradox a linear stability analysis is first performed on the jet in the modern day and the lgm simulation the latter has relatively strong barotropic velocity shear it was found that the lgm mean state is more unstable to baroclinic disturbances than the modern day mean state although the three dimensional jet structure does stabilize the lgm jet relative to the eady growth rate next feature tracking was used to assess the storm track seeding and temporal growth of distur

a review of cenozoic evolution of the southeastern united states atlantic coast north of the georgia trough abstract from late eocene or oligocene to the present the pattern of cyclic sediment deposition on the atlantic coastal plain of the southeastern united states is the product of 1 a relatively stable trailing edge continental margin with gentle downwarping 2 deposition of siliciclastics by major appalachian mountain and piedmont draining rivers and shelf generated carbonates 3 a humid temperate to subtropical climate 4 a mesotidal coast with moderate wave energy and periodic tropical storms 5 dominant longshore drift towards the southwest 6 a history of sea level change that was moderately submergent from late cretaceous through late eocene or oligocene and mildly emergent during the neogene intermittent fluctuations in sea level up to 100 m in the neogene subdivide the stratigraphy as unconformities during the late oligocene through holocene but are less pronounced in the paleogene each of these six factors has influenced the geomorphology sedimentation stratigraphy petrology and geometry of the cenozoic sedimentary units and the diversity of surficial quaternary coastal deposits during the quaternary sea level change would have been produced by glacial interglacial cycles the late eocene oligocene to early miocene and the late miocene transition experienced a major sea level decline influenced by ice cap formation in addition to climatic cycle induced sea level fluctuations

late pleistocene braided rivers of the atlantic coastal plain usa abstract infrared landsat imagery band 4 clearly reveals braided river patterns on late pleistocene terraces of unglaciated rivers in the atlantic coastal plain of the southeastern united states a region that presently exhibits meandering patterns that have existed throughout the holocene these pleistocene braided patterns provide a unique global example of river responses to late quaternary climate changes in an unglaciated humid subtropical region at 30 35 north latitude detailed morphological and chronological results are given for the oconee altamaha river valley in georgia and for the pee dee river valley in south carolina including 15 optically stimulated luminescence osl dates and four radiocarbon dates correlative examples are drawn from additional small to large rivers in south and north carolina osl and radiocarbon 14 c dates indicate distinct braiding at 17 30 ka within oxygen isotope stage 2 ois 2 and braiding probably existed at least during parts of ois 3 and possibly ois 4 back to ca 70 ka the chronology suggests that braiding is the more common pattern for the late quaternary in the southeastern united states braided terraces appear to have been graded to lower sea levels and are onlapped by holocene floodplain deposits up to 10 60 km from the coast the braiding probably reflects the response of discharge and sediment yield to generally cooler and drier paleoclimates which may have had a pronounced runoff season sedimentation of eolian dunes on the braid plains is coeval with braiding and supports the conclusion of dry soils and thin vegetation cover during the late pleistocene our chronological data contribute to a body of literature indicating that reliable osl age estimates can be obtained from quartz rich bed load sand from braided rivers based on good correlations with both radiocarbon dates from braided fluvial sediment and osl dates from stratigraphically correlative eolian sand

velocity and turbulence affected by submerged rigid vegetation under waves currents and combined wave current flows abstract vegetation can change flow structure and turbulence characteristics however few studies have focused on combined wave current flows in canopy with vertically varying density therefore laboratory experiments were carried out to investigate hydrodynamics affected by submerged rigid vegetation with different densities i e sparse dense and vertically varying density under waves currents and combined wave current flows in submerged canopy with vertically uniform density large shear stress occurs around the canopy top thus in the vertical distributions the greatest values of maximum wave velocity under pure waves and the greatest values of turbulent kinetic energy tke under unidirectional currents and combined wave current flows appear around the canopy top in canopy with vertically varying density the shear stress at each canopy top is relatively small resulting in the vertically smooth distributions of velocity and tke under pure waves while under unidirectional currents and combined wave current flows canopy scale turbulence throughout the entire water column occurs owing to the influence of multiple canopy tops an improved formula considering drag coefficient vegetation density and diameter was proposed to predict stem scale turbulence using characteristic velocity the formula is appropriate for vegetated flow in which stem scale turbulence is dominant and it can be further used as a simple method to assess tke for sediment or substances transport affected by vegetation

tracking the last sea level cycle seafloor morphology and shallow stratigraphy of the latest quaternary new jersey middle continental shelf seafloor geomorphology and surficial stratigraphy of the new jersey middle continental shelf provide a detailed record of sea level change during the last advance and retreat of the laurentide ice sheet 120 kyr b p to present a nw se oriented corridor on the middle shelf between water depths of 40 m the mid shelf paleo shore and 100 m the franklin paleo shore encompasses 500 line km of 2d huntec boomer profiles 500 3500 hz an embedded 4 6 km2 3d volume and a 490 km2 swath bathymetry map we use these data to develop a relative stratigraphy core samples from published studies also provide some chronological and sedimentological constraints on the upper 5 m of the stratigraphic succession the following stratigraphic units and surfaces occur from bottom to top 1 r a high amplitude reflection that separates sediment 46 5 kyr old by ams 14c dating from overlying sediment wedges 2 the outer shelf wedge a marine unit up to 50 m thick that onlaps r 3 channels a reflection sub parallel to the seafloor that incises r and appears as a dendritic system of channels in map view 4 channels fill the upper portion of which is sampled and known to represent deepening upward marine sediments 12 3 kyr in age 5 the t horizon a seismically discontinuous surface that caps channels fill 6 oblique ridge deposits coarse grained shelly units comprised of km scale shallow shelf bedforms and 7 ribbon floored swales bathymetric depressions parallel to modern shelf currents that truncate the oblique ridges and cut into surficial deposits we interpret this succession of features in light of a global eustatic sea level curve and the consequent migration of the coastline across the middle shelf during the last 120 kyr the morphology of the new jersey middle shelf shows a discrete sequence of stratigraphic elements and reflects the pulsed episodicity of the last sea level cycle r is a complicated marine non marine erosional surface formed during the last regression while the outer shelf wedge represents a shelf wedge emplaced during a minor glacial retreat before maximum wisconsin lowstand i e marine oxygen isotope stage 3 1 channels is a widespread fluvial subarial erosion surface formed at the late wisconsin glacial maximum 22 kyr b p the shoreline migrated back across the mid shelf corridor non uniformly during the period represented by channels fill oblique ridges are relict features on the new jersey middle shelf while the ribbon floored swales represent modern shelf erosion there is no systematic relationship between modern seafloor morphology and the very shallowly buried stratigraphic succession

sediment deposition from turbidity currents in simulated aquatic vegetation canopies a laboratory flume experiment was carried out in which the hydrodynamic and sedimentary behaviour of a turbidity current was measured as it passed through an array of vertical rigid cylinders the cylinders were intended primarily to simulate aquatic vegetation canopies but could equally be taken to represent other arrays of obstacles for example forests or offshore wind turbines the turbidity currents were generated by mixing naturally sourced poly disperse sediment into a reservoir of water at concentrations from 1 0 to 10 0 gl 1 which was then released into the experimental section of the flume by removing a lock gate for each initial sediment concentration runs with obstacle arrays with solid plant fractions of 1 0 and 2 5 and control cases with no obstacles were carried out the progress of the current along the flume was characterized by the array drag term cdaxc where cd is the array drag coefficient at the frontal area of cylinders per unit volume and xc the position of the leading edge of the current along the flume the downward depositional flux of sediment out of the current as it proceeded was measured at 13 traps along the flume analysis of these deposits divided them into fine 2 2 to 6 2 m and coarse 6 2 to 104 m fractions at the beginning of their development the gravity currents proceeded in an inertia dominated regime until cdaxc 5 for cdaxc 5 the current transitioned into a drag dominated regime for both fine and coarse sediment fractions the rate of sediment deposition tended to decrease gradually with distance from the source in the inertial regime remained approximately constant at the early drag dominated regime and then rose and peaked at the end of the drag dominated stage this implies that when passing through arrays of obstacles the turbidity currents were able to retain sufficient sediment in suspension to maintain their flow until they became significantly influenced by the drag exerted by the obstacles this article is protected by copyright all rights reserved

salt marsh sea level indicators and transfer function development for the magdalen islands in the gulf of st lawrence canada abstract late holocene salt marsh sediments allow the reconstruction of pre industrial relative sea level changes typically reconstructions are derived by quantifying a relationship between contemporary proxies and elevation which is then applied to down core fossil assemblages via a transfer function common sea level indicating proxies are salt marsh foraminifera and diatoms however testate amoebae represent an alternative complementary proxy with current sea level research increasingly invoking multi decadal timescale processes such as ocean current strength or wind stress to explain relative sea level changes there is a need for increased vertical precision in reconstructions this paper presents new surface assemblages of salt marsh foraminifera and testate amoebae with respect to elevation from two coastal locations in the magdalen islands in the gulf of st lawrence eastern canada we analyse the suitability of each proxy for reconstructing sea level using multivariate statistics ordination and regression modelling testate amoebae are found in greater abundance and diversity than foraminifera and their assemblage variations can be better accounted for by changes in elevation the contemporary training sets from the magdalen islands were able to predict marsh surface elevations viz sea level to precisions of 0 08 m and 0 12 m for testate amoebae and foraminifera respectively there were no benefits from combining the two proxies into a unified training set it was possible to improve the performance of the foraminifera based transfer function by incorporating a second dataset from newfoundland which served to increase the range of the sampled environment and improve the correlation coefficient between sample elevations and model predictions in accordance with existing literature we find transfer function performance to be better at locations with smaller tidal ranges

field observations and modelling of holocene sea level changes in the southern bay of biscay implication for understanding current rates of relative sea level change and vertical land motion along the atlantic coast of sw europe abstract the absence of basal peat in the stratigraphic sequences of the southern bay of biscay has long precluded the development of holocene sea level curves we have approached this problem by combining the indicative depositional meaning derived from the micropalaeontological composition and sand content with radiocarbon ages of 55 borehole samples obtained from three estuarine areas of the southern bay of biscay these new sea level index points have produced the first complete holocene sea level curve from this area we further reviewed all available sea level data from sw europe to provide the regional trend and use these data to calibrate a recently developed isostatic model field data and model reconstructions present a good agreement for the region considered a north south trend is apparent in the data and this is shown to be dominated by the influence of the deglaciation of eurasian ice sheets as suggested by previous studies for this region however some data model discrepancy in the south of the iberian peninsula suggests that local factors tend to dominate during the late holocene on comparing our results to estimates of recent sea level rise obtained from tide gauges and high resolution proxy records it is clear that this region has experienced a significant acceleration in sea level during the past century or so

identifying the causes of sea level change global mean sea level change has increased from a few centimetres per century over recent millennia to a few tens of centimetres per century in recent decades a review of the latest work shows that global mean sea level rise is unlikely to exceed one metre over the twenty first century but regional departures from this global mean could reach several decimetres

holocene crustal movements and sea level changes in great britain crustal downwarping has occurred throughout southern and south eastern england and most of wales for at least the last 4000 years but the type of movement in some areas of southern and eastern england is more complicated than simple linear subsidence highest estimated rates of subsidence since 4000 bp are for the thames estuary and norfolk up to 2 mm yr glacio isostatic processes have resulted in uplift in northern england and mainland scotland the rates of uplift have decreased throughout the holocene estimates for the present range from zero in south lancashire and the tees estuary to over 1 mm yr though less than 2 mm yr in central scotland over 400 sea level index points from the databank of 904 cases collected for igcp project 200 are grouped into 15 main areas and used to investigate the nature of crustal movements in great britain since 8800 bp but there are significant deficiencies in available data which constrain the analysis

relative sea level changes in the basque coast northern spain bay of biscay during the holocene and anthropocene the urdaibai estuary case abstract in order to reconstruct the environmental evolution process of the urdaibai estuary in response to sea level changes in the basque coast northern spain bay of biscay during the last 8500 years 10 boreholes were drilled in different estuarine areas using a rotary drill until the pre quaternary basement was reached one manual short core 50 cm was obtained from a salt marsh environment located in the middle part of the estuary micropalaeontological benthic foraminifera sedimentological grain size and geochemical 14 c 210 pb and 137 cs radioisotopes and total pb and zn analyses were performed on these materials aiming to quantify the sea level changes both of natural origin holocene or derived from recent human activities anthropocene based on the obtained results and by comparison with previously published information for this coastal area the holocene environmental evolution of the urdaibai estuary has been interpreted as the result of relative sea level variation that exhibits a rapid rise until 7000 cal bp followed by a moderate rise since then and a stabilization during the last 3000 years until modern rates of sea level rise 20th century 1 7 0 2 mm y 1 were reached

late quaternary sea level changes crustal movements and coastal evolution in northumberland uk northumberland lies in the transition between holocene emergence and submerg ence and is thus a critical zone for testing models of isostatic rebound we have collected data from this area to reconstruct relative sea level changes and lateral coastline movements for the last 14000 y these are deposits from tidal marsh back barrier wetland and terrestrial environ ments producing 47 sea level index points from 12 sites there is no unequivocal evidence for late devensian sea levels above present and the reliable sea level index points are restricted between 26 m and 12 5 m relative to present and 9 0 2 5 kyr cal bp analysis of these quantifies differential responses to glacio and hydroisostatic rebound with the northern sites recording a mid holocene sea level maximum ca 2 5 m above present whereas the southern sites show a maximum ca 0 5 m above present these observations show a reasonable fit with the predictions from quantitative models of glacio and hydroisostatic rebound but there is currently no unique solution of earth and ice model parameters that will explain all the sea level observations copyright 2000 john wiley sons ltd

experimental study on vegetation flexibility as control parameter for wave damping and velocity structure abstract vegetation can contribute to coastal defence by damping incoming waves however prior studies have shown that attenuation varies greatly among plant species plant flexibility is a mechanical property that is commonly omitted but varies considerably between shrubs and grasses on salt marshes therefore we present an experimental study in a laboratory wave flume with artificial vegetation that differs in flexibility only we measured wave attenuation and water particle velocities around rigid and flexible salt marsh vegetation waves were measured using a series of gauges and particle image velocimetry piv was used to measure spatio temporal variations of water particle velocities in the x z plane around the vegetation our results show that flexible vegetation attenuates waves up to 70 less than rigid vegetation due to swaying of flexible plants furthermore we find that rigid vegetation modifies the velocity structure whereas flexible vegetation does not specifically a mean current in the direction of wave propagation develops around the canopy and the horizontal particle velocities are amplified directly above the canopy these results indicate that plant flexibility is a key parameter in the wave vegetation interaction that controls wave damping and velocity structure

the impact of north atlantic storminess on western european coasts a review abstract instrumental and documentary records of storminess along the atlantic coast of western europe show that storm activity exhibits strong spatial and temporal variability at annual and decadal scales there is evidence of periods of increased storminess during the little ice age lia ad 1570 1990 and archival records show that these periods are also associated with sand movement in coastal areas independent evidence of sand movement during the lia is derived from dating the coastal sand deposits using luminescence or radiocarbon methods the holocene record of sand drift in western europe includes episodes corresponding to periods of northern hemisphere cooling particularly at 8 2 ka and provides the additional evidence that these periods like the lia were also stormy

the late holocene coastal dunefield at vejers denmark characteristics sand budget and depositional dynamics abstract the coastal dunefield at vejers west coast of jutland which is now stabilized by vegetation covers an area of approximately 120 km 2 and occurs in a very high energy wind regime along the coastline a narrow belt of 5 15 m high dune ridges occur the dune ridges are gradually replaced inland by 10 20 m high parabolic or irregular dune forms in the central part of the dunefield a large aeolian sand plain ca 50 km 2 occurs at the windward side of a large and up to 20 m high parabolic dune the 3d structure of the dunefield deposits have been studied by geomorphological analysis sedimentological facies analysis of borings trenches and natural exposures and most importantly by georadar mapping the aeolian deposits which overlie a middle to late holocene barrier spit depositional system can be divided into a lower unit that drapes the underlying barrier system topography and an upper unit that includes the present dunes the boundary between the two aeolian units is a well developed phragmites peat the lower aeolian unit is composed of two aeolian subunits separated by an organic rich horizon also the upper unit is composite and composed of a basal aeolian sand cover and overlying dune or sand plain deposits the dune deposits locally are composed of up to four depositional subunits separated by immature soils the base of the lower aeolian unit formed around 300 a d whereas the phragmites peat at the base of the upper aeolian unit has been dated to ca 1000 a d from historical sources we know that the present dunefield primarily formed between 1550 and 1850 a d the sand content in the upper unit is estimated to 550 10 6 m 3 which yields sand transport rates between 25 m 3 m width 1 yr 1 accumulation in 1000 years and 83 m 3 m width 1 yr 1 accumulation in 300 years the sand in the dunefield originated from beach deposits a large but pulsating supply of sand was supplied to the beaches by southwards running coastal currents the composition of the vejers dunefield deposits indicate that periods of dunefield growth alternated with periods of dunefield stabilization during the last ca 1700 years the final and most important phase of dunefield growth took place during the little ice age this period was characterized by an overall cold and stormy climate and a relative low sea level and resulted in an increased availability of sand in the shorezone and a high influx of sand into the dunefield short periods of decreased storminess are recorded by the immature soils dunefield growth prior to 1000 a d was also linked to cold and stormy climatic intervals

sea level change along the french mediterranean coast for the past 30 000 years abstract observational evidence for sea level change along the french mediterranean coast has been examined and compared with glacio hydro isostatic models to predict the spatial and temporal patterns of change for about the past 30 000 14c years these predictions are pertinent to discussions of changing ocean volumes during this interval the tectonic stability or otherwise of the coastal areas mantle rheology and the timing of possible human occupation of the now submerged coastal plain and caves such as cosquer cave near marseille the principal results from the analysis are i sea levels along this section of the coast have risen continually since the time of the last glacial maximum lgm and at no time during the holocene has the mean sea level been higher than that of today ii the coast has been tectonically stable between marseille and nice as well as further to the west in roussillon western corsica may have experienced a slow tectonic uplift of between 0 15 0 3 mm year for the past 3000 years but northernmost corsica appears to have been stable during this same interval iii during the lgm sea levels along the coast and immediate off shore areas stood at between 105 115 m below present level the range reflecting the importance of the isostatic contributions during oxygen isotope stage 3 sea levels do not appear to have risen locally above about 60 m iv the rebound parameters describing the mantle rheology and ice sheets required to match the limited observational evidence are consistent with the results of similar analyses carried out for other parts of europe because of its distance from the former northern ice sheets the isostatic factors are particularly sensitive to the value of the lower mantle viscosity v the model predictions for sea level change at the cosquer cave site and for its immediate environments indicate that the cave was last readily accessible before about 10 700 500 14c years about 12 500 500 cal years bp and that the cave entrance was completely flooded by 9000 200 radiocarbon years bp between about 9800 and 10 300 calibrated years bp the cave was above sea level throughout the oxygen isotope stage 3

late quaternary sea level change in south africa abstract a late quaternary sea level curve for south africa is presented on the basis of new and published data from a range of sea level indicators and a variety of locations available evidence suggests that sea level in south africa broadly follows that described from the caribbean but that deviations occur during sea level highstands during the last interglaciation oxygen isotope stage 5 and the late holocene coastal emergence produced higher sea levels in south africa than those identified in the caribbean during the same time intervals this is tentatively ascribed to predicted lithospheric deformation in continental margin settings

salt marsh reconstructions of relative sea level change in the north atlantic during the last 2000 years abstract sea level changes record changes in the mass balance of ice sheets and mountain glaciers as well as dynamic ocean atmosphere processes unravelling the contribution of each of these mechanisms on late holocene timescales ideally requires observations from a number of sites on several coasts within one or more oceans we present the first 2000 year long continuous salt marsh based reconstructions of relative sea level rsl change from the eastern north atlantic and uniquely from a slowly uplifting coastline we develop three rsl histories from two sites in north west scotland to test for regional changes in sea level tendency a positive tendency indicating an increase in the proximity of marine conditions and a negative tendency the reverse whilst at the same time highlighting methodological issues including the problems of dataset noise when applying transfer functions to fossil salt marsh sequences the records show that rsl has been stable 0 4 m during the last two millennia and that the regional sea level tendency has been negative throughout most of the record lengths a recent switch in the biostratigraphy of all three records indicating a regional positive tendency means we cannot reject the hypothesis of a 20th century sea level acceleration occurring in north west scotland that must have exceeded the rate of background rsl fall 0 4 mm yr 1 but this signal appears muted and later than recorded from the western north atlantic

gulf trough the atlantic connection analyses of seismic reflection profiles and stratigraphic data indicate a continuation of the gulf trough trend across eastern south carolina and offshore between cape fear and cape hatteras north carolina seismic profiles show a linear northeast trending zone of nondeposition and erosion and areas of chaotic deposition in the eocene and oligocene sections the character of deposition and erosion along this trend is similar to that produced by bottom currents under the core of the present gulf stream the trend separates deep water from shallower water deposits indicating that the erosion was produced by strong marine currents flowing through the gulf trough in the high sea levels of middle eocene through early oligocene time

origin evolution and distribution of shoreface sand ridges atlantic inner shelf u s a abstract a computer mapping system was employed to document the location of 259 shoreface attached and detached sand ridges in water although shoreface attached sand ridges appear to have several different modes of formation a two step process for the development of most shoreface attached and detached sand ridges along u s atlantic barrier island and cape coastlines is proposed 1 sand is deposited as ebb tidal deltas or river deltas along the lower shoreface and or inner continental shelf prior to or during transgression followed by 2 further transgression which reworks the deltaic sand bodies into linear sand ridges at the base of the shoreface by shelf processes the best developed shoreface sand ridge fields along the u s atlantic shelf lie adjacent to shorelines characterized by all of the following 1 transgression 2 mixed energy wave dominated barrier islands and 3 laterally migrating tidal inlet systems tidal inlet systems are natural sediment sinks that capture sand carried by longshore sediment transport ebb tidal delta deposits associated with these migrating tidal inlets provide the initial sand body for the development of shoreface attached sand ridges the oblique orientation and linear form of shoreface attached sand ridges appear to be a function of shoreline transgression lateral inlet migration and wave reworking of ebb tidal delta deposits concentrated along an ebb tidal delta retreat path shelf processes act as modifying agents in the evolution of sand ridges during and after ebb tidal delta deposition in general shoreface attached sand ridges are poorly developed or absent along eroding headlands spits and barrier island shorelines characterized by naturally stabilized tidal inlets these latter inlets and shoreline types are dominated or influenced by one or all of the following 1 antecedent topography 2 higher tidal ranges 3 larger tidal prisms 4 lower wave energies or 5 finer grain sizes the coupling of shoreline and shallow marine sedimentary processes during a transgression is critical to the origin evolution and distribution of shoreface sand ridges in the study area modern shoreface attached sand ridges are also known to occur in different coastal and shelf settings where large amounts of sediment were supplied to the shoreface and inner shelf during or immediately before transgression commonly observed vertical and lateral interrelationships of holocene shoreface attached sand ridges and tidal inlets or distributary channels have important ramifications for the development of shelf sandstone facies models in addition the geometric relationship documented in this study provides predictive petroleum and hard mineral exploration models of the spatial and temporal distribution of shoreface and shelf sand ridges

temporal variation of accumulation rates on a natural salt marsh in the 20th century the impact of sea level rise and increased inundation frequency abstract salt marshes are potentially threatened by sea level rise if sediment supply is unable to balance the rising sea a rapid sea level rise is one of the pronounced effects of global warming and global sea level is at present rising at an elevated rate of about 3 4 mm y 1 on average this increasing rate of sea level rise should make it possible to study the effect of rapidly rising sea level on salt marsh accumulation however such an understanding is generally hampered by lack of available data with sufficient precision here we present a high precision dataset based on detailed radiometric measurements of 137cs in 10 sediment cores retrieved at a natural and unmanaged micro tidal salt marsh two distinct 137cs peaks were found in all cores one peak corresponding to the 1963 maximum caused by testing of nuclear weapons in the atmosphere and the other to the chernobyl accident in 1986 salt marsh accretion has generally kept pace with sea level rise since 1963 but comparison of the accumulation rates of minerogenic material in the period 1963 1986 and 1986 2003 revealed a slight decrease in accumulation with time in spite of an observed increase in inundation frequency the observed decrease in sediment deposition is significant and gives reason for concern as it may be the first sign of a sedimentation deficiency which could be threatening this and other salt marshes in the case of a rapidly rising sea level our work demonstrates that the assumption of a constant relationship between salt marsh inundation and sediment deposition is not necessarily valid even for a salt marsh that receives most of its allocthonous sediment from the adjacent sea the apparent decrease in sediment deposition indicates that the basic assumption of sufficient sediment supply used in contemporary models dealing with salt marsh accretion is most probably not valid in the present case study and it may well be that this is also the case for many other salt marshes especially if sea level continues to rise rapidly as indicated by some climate change scenarios

modified hydrodynamics in canopies with longitudinal gaps exposed to oscillatory flows summary longitudinal gaps are commonly found in aquatic canopies while the ecological significance of gaps may be large we know little about their impact on the hydrodynamics within the canopy we used laboratory experiments to investigate the effect of longitudinal gaps within canopies exposed to a wave field in rigid submerged and emergent vegetation wave velocities were reduced compared to the case without vegetation flexible canopies also attenuated waves but this attenuation was lower than for rigid canopies the presence of the gap modified the mean current associated with the waves in both the gap and the lateral vegetation a gap within a canopy of 5 solid plant fraction did not show differences in the wave attenuation between the gap and the lateral vegetation in contrast gaps within canopies of 10 solid plant fraction resulted in large differences between the gap and the lateral vegetation in all the experiments the effect of a gap within a canopy reduced the wave attenuation within the lateral vegetation adjacent to the gap when compared with a canopy without a gap in canopies with rigid plants the lateral vegetation modified the wave attenuation in the nearby gap in contrast the lateral flexible vegetation did not produce any effect on the wave attenuation of the adjacent gap canopy density plant height and plant flexibility were critical for determining the hydrodynamics throughout the canopy and in the gap

late pleistocene and holocene environments of the southeastern united states from the stratigraphy and pollen content of a peat deposit on the georgia coastal plain abstract a 5 4 m peat core from the sandy run creek src valley in the upper coastal plain of georgia shows that before 30 ka the valley had an aggradational sandy floor with shallow swales and low ridges of 1 2 m amplitude suggesting a braided stream pattern and a low water table the climate from 30 25 ka was cool and dry and the vegetation open grassland with stands of pine and spruce that produced few fires at ca 16 ka a warmer wetter climate caused src to meander and incise the valley fill removing some previously deposited sediment at the site of our peat core so that sediments of 13 ka rest directly on sediments deposited at 25 ka after ca 13 ka higher groundwater levels initiated vertical accretion of floodplains allowing peat accumulation in shallow depressions across the valley pollen from the younger dryas period ca 13 11 ka indicates a cool moist environment of open oak woodland mesic trees riparian populations of alder and reduced levels of pine by the early to mid holocene tupelo and oak dominated over pine indicating wetter conditions while sand stringers in peat record periodic heavy rains an elevated water table and intervals of substantial runoff cooling after ca 4 5 ka brought drier and more variable conditions fires increased and southern pine replaced tupelo and oak the absence of sand stringers in peat younger than 4 5 ka indicates fewer intense rainfall events

on the origin of late holocene sea level highstands within equatorial ocean basins abstract late holocene sea level highstands of amplitude 3 m are endemic to equatorial ocean basins these highstands imply an ongoing and moderate sub mm yr sea level fall in the far field of the late pleistocene ice cover that has long been linked to the process of glacial isostatic adjustment gia clark et al 1978 mitrovica and peltier 1991 coined the term equatorial ocean syphoning to describe the gia induced sea level fall and they provided the first physical explanation for the process they argued that water migrated away from far field equatorial ocean basins in order to fill space vacated by collapsing forebulges at the periphery of previously glaciated regions we provide a complete physical explanation for the origin of equatorial ocean syphoning and the associated development of sea level highstands using numerical solutions of the equation that governs meltwater redistribution on spherical viscoelastic earth models in particular we separate the total predicted sea level change into contributions associated with ice and meltwater loading effects and by doing so isolate a second mechanism that contributes significantly to the ocean syphoning process ocean loading at continental margins induces a levering of continents and a subsidence of offshore regions that has also long been recognized within the gia literature walcott 1972 we show that the influx of water into the volume created by this subsidence produces a sea level fall at locations distant from these margins indeed over the major ocean basins that is comparable in amplitude to the syphoning mechanism isolated by mitrovica and peltier 1991

tests of glacial rebound models for fennoscandinavia based on instrumented sea and lake level records summary evidence for changing sea levels in northwestern europe related to glacial rebound is found in both the geological record of the past millennia and in the instrumental records of the past two centuries the latter records are of two types records of sealevel change primarily from the baltic and the gulfs of finland and bothnia and records of the tilting of some of the larger lakes in both finland and sweden the sealevel records are particularly important because of their long duration and high quality their large number and good spatial distribution and the spatially coherent background noise the two instrumental data types are complementary and provide constraints on the upper mantle rheology and on the distribution of ice during the late glacial stage comparisons of the observed rates of change of the water levels with models for glacial rebound yield earth models with a lithospheric thickness of 80 100 km and an uppermantle viscosity of 4 5 1020 pa s evective parameters that are consistent with those obtained from the analysis of the geological evidence for the same region the mareograph results support ice sheet models in which the late weichselian ice thickness over the eastern and southern parts of fennoscandia is relatively thinner than that for the western region also consistent with the interpretation of the geological evidence for sea level change in addition the instrumental records provide constraints on the eustatic sea level change for about the past 100 years a satisfactory separation of the earth rheology parameters from this rate of change can be achieved by estimating the latter only from those records for which the predicted isostatic evects are small a check on these results is possible by using the lake level records to establish constraints on the earth model parameters and the sea level records to constrain also the eustatic change all approaches lead to an average eustatic sea level rise for the past century of about 1 1 0 2 mm yr 1

long term variations in backbarrier salt marsh deposition on the skallingen peninsula the danish wadden sea abstract accretion on a natural backbarrier salt marsh was determined and modeled as a function of high tide level initial salt marsh level and distance from the salt marsh edge accretion measurements were based on up to 67 year old marker horizons supplemented by 210pb 137cs datings the salt marsh is situated on the backbarrier of the skallingen peninsula in the northern part of the danish wadden sea the tidal range mean 1 5 m is strongly affected by wind tide which occasionally adds up to about 3 m to the astronomical high tide level accretion is restricted to a narrow vertical band from about 0 1 m below to about 0 7 m above the mean high water level in the outer part of the backbarrier close to the tidal flat mean accretion is about 4 mm yr 1 and in the inner part it is about 2 mm yr 1 the decrease takes place in a similar manner as the decrease across a flood plain the major part of salt marsh accretion is associated with high water levels corresponding to weather conditions characterized by gales the long term variation of salt marsh accretion correlates with variations in the north atlantic oscillation winter index the number of over marsh high tides decreases exponentially with high tide level the function constants controlling this distribution vary in direct ratio to the mean sea level plausible near future scenarios of tidal development were obtained by extrapolating this relation three sea level scenarios were tested i sea level rise continues at a constant long term rate of 2 3 mm yr 1 ii sea level rise continues at a constant short term rate of 4 2 mm yr 1 and iii sea level rise accelerates to a constant rate of 6 4 mm yr 1 in the first case accretion on the salt marsh will keep pace with the high water level rise in the second case deposition in the inner part of the salt marsh will lag behind while that of the outer part of the salt marsh will keep pace with the rising high water level in the third case corresponding to a worst case scenario for the 21th century the salt marsh will gradually drown

continental shelf landscapes of the southeastern united states since the last interglacial abstract the wide sediment starved continental shelf and modern coastal areas of the southeastern united states retain well preserved but scattered remnants of a submerged paleolandscape this paper presents a conceptual model of stratigraphic deposition and landscape formation since the last interglacial on the continental shelf of south carolina with portions of north carolina georgia and florida usa data for this study include multibeam bathymetry surveys sidescan sonar mosaics high resolution subbottom profiles and ground truth surveys from 250 m to the modern tidewater region four bathymetric zones are recognized with eleven landforms and landform indicators the described zones range in depths from the modern shoreline across the shelf and over the shelf edge to 250 m msl relative sea level curves are presented for the area and discussed in conjunction with cultural and climatic events the potential for preservation of paleoamerican sites is high at the shelf edge between 130 m and 45 m with archaic and later occupations likely in depths of less than 25 m prominent vantage points for paleoamericans 11 kya would have existed at the shelf edge and tidewater resources would have been available nearby for a period of almost 6 ka rapid transgression rates 60 km ka after the sea level rose over the shelf edge make preservation of tidewater sites less likely on the outer and middle shelf searches for the earliest paleoamericans should focus on promontories at the edge of the shelf and along future discoveries of paleoincisions on the shelf mapping and delineating this paleolandscape and associated unconsolidated sedimentary deposits interspersed with rocky plains and ledges will continue to be a priority to marine archeologists coastal managers fishery scientists and marine spatial planners over the next several decades

geoarchaeological records in temperate european river valleys quantifying the resource assessing its potential and managing its future throughout the quaternary episodes of glaciation and associated low sea level have resulted in the connection of the terrestrial landmasses of britain and mainland europe the river systems that established themselves across these newly emergent land surfaces of the coastal plain would have created important migration corridors for both animals and humans a point corroborated by the affinity of palaeolithic remains across britain and europe technological developments within the last decade have allowed these now submerged valley floors and adjacent terrestrial landscapes associated with the last cold stage and early and middle parts of the current holocene interglacial to be explored and their archaeological legacies unravelled providing geoarchaeologists with an opportunity to contribute to major cultural debates however in order to maximize knowledge it is essential that geoarchaeologists working within river valleys across both britain and the european continent are addressing similar research questions by collecting data using comparable methodologies this paper reviews the approach taken in different regions and provides a baseline assessment to allow the development of a coherent european wide framework for alluvial geoarchaeology and geoprospection particularly with respect to the holocene record

the anatomy of interglacial sea levels the relationship between sea levels and ice volumes during the last interglacial abstract the elevations and chronology of interglacial shorelines and other sea level indicators provide information on ice volumes for these earlier periods compared with today but as for the holocene the relationship between sea levels and ice volumes for earlier interglacials is not simple because of the planet s deformational gravitational and rotational response to changes in ice water loads glacio hydro isostasy in particular the pattern of global sea level for a particular interglacial will be a function of the earth and ocean response to ice loads applied before during and after the interglacial in question this paper examines the role of glacio hydro isostasy during these glacial cycles to make three key points the first is to demonstrate why interglacial sea levels cannot be interpreted directly in terms of ice volume the second is to illustrate the spatial variability that can be expected in interglacial sea levels because of the earth s isostatic response to changing ice and water loads and to demonstrate why observations from different localities should not be combined into a single sea level function without first correcting for differential isostatic effects the third addresses the question whether in the absence of perfect knowledge of the ice sheets and earth rheology inferences can be made about ice volumes during an interglacial we conclude that if these isostatic factors are ignored interpretations of interglacial sea levels can lead to serious errors in the inferences about ice volumes during the interglacials

keel depths of modern antarctic icebergs and implications for sea floor scouring in the geological record abstract icebergs affect the geological record through the scouring or ploughing action of their keels reworking sediments where they contact the sea floor satellite radar altimeter measurements of the surface elevation of the marine margins of the antarctic ice sheet are inverted to produce ice thickness values these data are assumed to represent the keel depths of newly calved icebergs there are three peaks in the frequency distribution of antarctic iceberg keel depths a about 140 200 m in thickness associated with smaller ice shelves fringing antarctica e g wilkins george vi and brunt ice shelves b about 250 300 m from large ice shelves e g ross ronne amery and c approximately 500 600 m from fast flowing ice sheet outlet glaciers e g pine island and dibble glaciers together with the filchner ice shelf controls on iceberg keel depth are ice thickness at the grounding line creep thinning and the rate of melting freezing at the floating ice shelf base with distance to the calving margin the distribution of sea floor scours produced by iceberg grounding is dependent on the changing form and flow of the glaciers and ice sheets from which icebergs are derived and on berg drift tracks and melt rates sea floor evidence for icebergs with particularly deep keels has sometimes been interpreted to indicate the presence of extensive former ice shelves however the largest modern antarctic ice shelves do not produce large numbers of icebergs thicker than about 350 m implying that sea floor scours found in deeper water are unlikely to be an indicator of extensive past ice shelf development iceberg scours found at water depths in excess of about 500 m in the geological record are instead probably indicative of either a the former presence of fast flowing ice sheet outlet glaciers b ice shelves fed from major interior basins where lateral spreading is constrained topographically or c a pulse of large icebergs released during major deglaciation or ice sheet collapse

sea level change glacial rebound and mantle viscosity fornorthern europe northwestern europe remains a key region for testing models of glacial isostasy because of the good geological record of crustal response to the glacial unloading since the time of the last glacial maximum models for this rebound and associated sea level change require a detailed knowledge of the ice sheet geometry including the ice thickness through time existing ice sheet reconstructions are strongly model dependent and inversions of sea level data for the mantle response may be a function of the model assumptions thus inverse solutions for the sea level data are sought that include both ice and earth model parameters as unknowns sea level data from fennoscandia the north sea the british isles and the atlantic and english channel coasts have been evaluated and incorporated into the solutions the starting ice sheet for fennoscandia is based on a reconstruction of a model by denton hughes 1981 that is characterized by quasi parabolic cross sections and symmetry about the load centre both global northwestern europe as a whole and regional subsets of the data solutions have been made for earth model parameters and ice height scaling parameters the key results are as follows 1 the response of the upper mantle to the changing ice and water loads is spatially relatively homogenous across scandinavia the north sea and the british isles 2 this response can be adequately modelled by an effective elastic lithosphere of thickness 65 85 km and by an effective upper mantle viscosity from the base of the lithosphere to the 670 km depth seismic discontinuity of about 3 4 1020 pa s the effective lower mantle viscosity is at least an order of magnitude greater 3 the ice thickness over scandinavia at the time of maximum glaciation was only about 2000 m much less than the 3400 m assumed in the denton hughes model 4 the ice profiles are asymmetric about the centre of the ice sheet with those over the western part being consistent with quasi parabolic functions whereas the ice heights over the eastern and southern regions increase much more slowly with distance inwards from the ice margin

lateglacial and holocene coastal evolution in the minho estuary n portugal implications for understanding sea level changes in atlantic iberia the absence of accurate sea level index points in sw europe has long precluded the development of holocene sea level curves and the correct understanding of tectonic activity in order to understan

a preliminary sediment budget for the winyah bay estuary south carolina usa abstract winyah bay a 65 km2 coastal plain estuary in south carolina has an average freshwater input of 557 m3 s 1 and presently receives 0 43 106 t yr 1 of suspended sediments from its watershed corresponding to a yield of 12 7 t km 2 yr 1 however 20 dams have been constructed on the upper rivers primarily on the yadkin and pee dee rivers which serve to capture an additional 0 40 106 t yr 1 of sediment implying a gross sediment yield of 24 5 t km2 yr 1 for the watershed although almost 50 never reaches the coast continuous dredging in the estuarine channels removes 0 107 106 t yr 1 of silt and clay from the estuary sediment coring and 210 pb analysis indicate that the sedimentation rate in mud bay a high accretion area in the lower estuary is 5 5 mm yr 1 which together with previous estimates of marsh sedimentation rates of 2 7 mm yr 1 in the tidal marshes surrounding the estuary leads to a total estuarine mud sedimentation estimate of 0 24 106 t yr 1 thus 80 of the fine grained sediment reaching winyah bay is either accumulating in adjacent marshes or on estuarine mud flats or is being dredged and deposited offshore although these budget calculations need further confirmation by direct measurements and additional coring winyah bay apparently delivers only a minimal amount of suspended fine grained sediments to the coastal ocean

flow structure in canopy models dominated by progressive waves summary laboratory experiments were carried out to study the flow structure both inside and above different canopy models which were dominated by progressive waves a set of experimental conditions were considered in a laboratory flume three vegetation models submerged rigid submerged flexible and emergent rigid three plant densities 128 640 and 1280 stems m 2 and three wave frequencies f 0 8 1 and 1 4 hz the progressive waves followed the second order stokes theory in the intermediate depth range the observations revealed that submerged and emergent rigid vegetation models modified the wave induced velocities i e both mean current and wave velocity the submerged rigid vegetation model for plant densities higher than 640 plants m 2 and wave frequency higher than 1 hz acted akin to a false floor confining the mean current to above the plant bed a penetration depth around 2 cm below the top of submerged rigid vegetation was found for the other runs the vertical profile of mean current did not present changes with respect to runs without plants the emergent rigid vegetation model reversed the direction of the induced mean current with the highest velocity corresponding to the highest plant density in contrast the submerged flexible vegetation model had a weak effect on the mean current with the vertical velocity profile similar to that found in experiments without vegetation the wave velocities inside the vegetation for the densest submerged rigid vegetation were found to be reduced by 20 when compared to the wave velocities without vegetation while in emergent rigid vegetation this reduction was of 45

accumulation of fine grained material in a danish tidal area abstract the exchange of fine grained material m between the north sea and the tidal area of gradyb in the danish wadden sea has been determined by means of the 210 pb dating method the amount of fine grained material accumulating in the area 169 km 2 has been calculated to be 142 10 3 t yr 1 of this approximately 85 is derived from the north sea 5 6 from rivers 4 from internal coastal erosion and another 5 6 from the combined effect of waste atmospheric deposition and net primary production these results have been verified through a budget for excess 210 pb it is demonstrated that fine sediments from the north sea are sorted before accumulating in the wadden sea with the result that the deposited material contains more coarse silt and less clay than is found in the source material from the north sea the relation between accumulated fine grained material and the volume of exchanged water is found to be in the same order of magnitude in gradyb as in jadebusen and dollard this relation is suggested to be a characterising parameter of the sedimentation in tidal areas

late quaternary climates and river channels of the atlantic coastal plain southeastern usa abstract late quaternary river patterns and sedimentation styles reflect past climate changes in atlantic drainages of eastern georgia and the carolinas past climate episodes for the region are summarized from pollen and eolian sedimentary records that exhibit correlation to major changes in river channel patterns records of past river responses are derived from luminescence and radiocarbon dated landforms and strata slow tectonic uplift does not explain temporal changes in channel patterns drainage networks have not received meltwater from continental or mountain glaciers eustatic influence would have been most pronounced on the now submerged continental shelf prior to 6 ka and currently manifests only within 60 80 km of the present highstand shoreline human impact overshadows climatic changes during historic time but was negligible during prehistoric time the late quaternary fluvial system primarily responded to climatic fluctuations that drove changes in vegetation precipitation and runoff patterns prehistoric meandering paleochannels of the holocene stand as important references to guide natural channel rehabilitation efforts during the coldest climate phases of the late wisconsin stage ca 30 16 ka when forest vegetation was sparse and interspersed with grasses and herbs many rivers and streams were braided with eolian dunes on the floodplains the terminal wisconsin stage ca 16 11 ka exhibited rapid warming and forest expansion characterized by pronounced change from braided to meandering patterns with intermediate forms of sandy scroll bar patterns the younger dryas cold excursion is not readily apparent in the regional fluvial record unusually large meandering channels of the terminal wisconsin stage continue into the first half of the holocene and indicate significantly larger bankfull flood discharges during those times than during the last half of the holocene bankfull channels during the last half of the holocene retained meandering patterns but decreased to modern like dimensions suggesting more modern like flood regimes no clear fluvial response occurs to the presumed middle holocene climatic optimum hypsithermal the medieval warm period and little ice age or to recent instrumentally observed fluctuations in climate but little research has been done in these realms

on eustatic sea level history last glacial maximum to holocene abstract this paper addresses the question of the magnitude and time dependence of the globally averaged eustatic rise of sea level that occurred subsequent to the time of last glacial maximum lgm at approximately 21 000 calendar years before present through the analysis of relative sea level rsl histories predicted by a realistic mass conserving and gravitationally self consistent theory of postglacial sea level change it is demonstrated that there are preferred oceanic locations at which this eustatic function is well approximated by local sea level history one such location is the island of barbados in the caribbean sea a site from which a coral based record exists that extends from mid holocene to lgm because of the sea level ambiguity that is inherent to coral based records however it is important that the global ice equivalent eustatic sea level curve inferred on the basis of the barbados data be tested against observations at other locations from which similarly extensive records are also available but which are derived on the basis of sea level indicators which are not subject to the ambiguities inherent to corals it is shown that when the eustatic function employed in the global theoretical model is tuned so as to enable the model to fit the barbados observations where the maximum relative sea level rsl depression is assumed to be near 120 m then the theory misfits the record from the sunda shelf in the indonesian archipelago as well as the record from j bonaparte gulf in northern australia both of these recently published records appear to constrain the lgm low stand of rsl to a value above 120 m the implications of these results for interpretation of the long coral derived records from the huon peninsula of papua new guinea and the island of tahiti are also discussed

relative sea level change and postglacial isostatic adjustment along the coast of south devon united kingdom previous sea level studies suggest that southwest britain has the fastest subsiding coastline in the united kingdom but tide gauge data gps and gravity measurements and geophysical models show little evidence of anomalous subsidence in this region in this paper we present 15 new sea level index points from four coastal barrier systems in south devon eight are from compaction free basal sediments and others were corrected for autocompaction our data suggest that relative sea level along the south devon coastline has risen by 21 4 m during the past 9000 years sea level rise slowed during the middle and late holocene and a rise of 8 1 m has occurred since ca 7000 cal yr bp anomalous ages for many rejected points are attributed to sediment reworking during barrier transgression the relative sea level history during the early and middle holocene shows a good fit with geophysical model predictions but the geological and modelled data diverge in the later holocene unlike the geophysical models sea level index points cannot differentiate between late holocene relative sea level histories of south devon and southwest cornwall it is suggested that this discrepancy can be resolved by obtaining additional high quality sea level index points covering the past 4000 years copyright 2008 john wiley sons ltd

modeling flow in coral communities with and without waves a synthesis of porous media and canopy flow approaches both canopy flow and porous media theories have been developed independent of one another to predict flow through submerged porous structures these approaches are very similar albeit with some key differences in how canopy resistance forces are parameterized canopy models provide a means of parameterizing the shear stresses that occur at the top of the canopy whereas porous media models can often provide a simpler and more tractable way of parameterizing turbulent form drag based on simple morphological metrics and empirical relationships already in the hydrology literature we developed a set of equations combining aspects of both models and applied this hybridized model to predict the flow structure within an experimental canopy formed by the branching coral porites compressa using model parameter values obtained from the literature results from the model predictions agreed well with direct measurements of flow speed and flow forces derived from particle image velocimetry under conditions of both unidirectional and wave driven oscillatory flow

aeolian sand movement and relative sea level rise in ho bugt western denmark during the little ice age this study documents an extensive aeolian sand sheet buried in the salt marshes of the ho bugt embayment in western denmark the extent of the sand sheet was mapped from c 60 cores and sections which were also used to reconstruct late holocene changes in relative sea level based on diatom analyses chronology was provided by optically stimulated luminescence osl and radiocarbon dating our study shows that since 2000 cal yr bp relative sea level in ho bugt has risen by approximately 1 5 m the overall rise was punctuated by two periods with higher than average rates of sea level rise the first between 2000 and 1400 cal yr bp and the second commencing c 500 cal yr bp around 700 cal yr bp the evolution of the skallingen spit may have been responsible for a reduction in the local tidal range and the formation of an extensive black layer in the western part of the embayment osl analyses date the sand sheet to between ad 1460 40 and ad 1550 30 490 40 and 400 30 cal yr bp consistent wi

mass transfer limitation of nutrient uptake by a wave dominated reef flat community maximum rates of phosphate nitrate and ammonium uptake by a reef flat community were estimated from rates of frictional dissipation that were calculated from the attenuation of waves propagating over the kaneohe bay barrier reef flat time averaged flow speeds across the entire study area ranged from 0 08 to 0 22 m s 21 observed decreases in wave energy fluxes and near bottom orbital velocities gave a mean estimate for the bottom friction coefficient cf of 0 22 6 0 03 friction coefficients were used to estimate nutrient mass transfer coefficients of 5 9md 21 for phosphate and 9 16 m d 21 for ammonium and nitrate wave heights offshore of kaneohe bay were also used to estimate an annual phosphate mass transfer coefficient of 8 6 2md that was determined from measured changes in phosphate concentrations across the reef flat we conclude that rates of phosphate uptake by the kaneohe bay barrier reef flat community are occurring near the limits of mass transfer net primary production is a major pathway by which mass and energy flow into coral reef ecosystems the uptake of dissolved nutrients is often the rate limiting step for net pri mary production in marine ecosystems thus a knowledge of the kinetics of nutrient uptake by coral reef communities is necessary for assessing how nutrient loading rates change in response to natural or anthropogenic increases in nutrient concentrations bilger and atkinson 1992 proposed that nutrient uptake by shallow reef communities was limited by mass transfer the physical transfer of nutrients across con centration boundary layers covering the surfaces of reef au totrophs these authors used mass transfer correlations for rough surfaces taken from the engineering literature to cor relate maximum rates of nutrient uptake with the frictional characteristics of experimental reef communities subse quent studies demonstrated the ability of such mass transfer correlations to predict nutrient uptake kinetics for experi mental reef communities within closed recirculating flumes atkinson and bilger 1992 bilger and atkinson 1995 thomas and atkinson 1997 and a large experimental me socosm atkinson et al 2001 the results of these studies made it clear that shallow water reef communities are ca pable of taking up nutrients from the water column at rates that are limited by mass transfer however it had not yet been demonstrated whether in situ rates of nutrient uptake

modeling the contribution of m2 tidal amplification to the holocene rise of mean high water in the gulf of maine and the bay of fundy abstract increase in the m2 principal lunar semi diurnal component of the tidal range is an important contributor to the postglacial rise of the high tide level in the gulf of maine and the bay of fundy in addition to relative sea level rise the increase occurred as the shape of this semi enclosed embayment changed with sea level rise and its natural period approached resonance with the m2 tide a three dimensional tide model 3dens predicts the following m2 tidal ranges averaged for the gulf of maine bay of fundy as a percentage of the present range 54 59 at 7000 yrs b p 73 at 5000 yrs b p 78 at 4000 yrs b p 85 at 3000 yrs b p 94 at 2000 yrs b p and 98 at 1000 yrs b p with a predicted sea level rise of 0 15 0 90 m by the year 2100 m2 tidal range may increase 0 3 1 9

modelling the glacial isostatic adjustment of the uk region the glacial isostatic adjustment of the uk region has been considered in a number of recent studies we have revisited this problem in order to i highlight some key issues with regard to limitations in the ice modelling approach adopted in these studies and ii consider the constraints provided from observations of crustal motion available via continuous global positioning system monitoring with regard to the first aim we have found that i previous studies have significantly overestimated ice thicknesses in regions where trim line field constraints were adopted and ii the duration of the glaciation phase of the uk ice sheet is a critical aspect of the model and that discrepancies in this model component have led to inconsistent inferences of earth model parameters with regard to the second aim we have found that predictions of horizontal velocities relative to a chosen site based on a uk ice model calibrated to fit the regional sea level database capture the geometry of the signal well but only account for 10 of the magnitude for a range of earth models

global to local scale parameters determining relative sea level changes and the post glacial isostatic adjustment of great britain abstract observations of relative sea level rsl change in great britain since 16 kyr bp and models of post glacial isostatic adjustment provide constraints on reconstructions of the british and antarctic ice sheets from the last glacial maximum to the present we use the global model from an earlier investigation modified ice 4g vm2 with lithospheric thickness 90 km which gives good rsl fits globally as well as for much of the british data a revised ice model for great britain that fits with recently published observations on ice limits and heights fails to explain all the misfits between rsl observations and predictions much more significant improvements result from models that incorporate a different chronology for the partial deglaciation of antarctica while keeping the total ice melt 17 m the same as in ice 4g vm2 the results suggest antarctic melting of 3 m ice equivalent sea level by 15 kyr bp only 1 m contribution to the 24 m rise of mwp1a with the major melting 12 5 kyr bp and a small amount of melting 1 0 0 3 m between then and 3 or 2 kyr bp these modifications produce rsl predictions for barbados that show the major changes in rate of sea level rise but with an offset up to 1 kyr compared to the observations possible explanations that remain to be investigated further are a delay in the melting of ice from some other region a reduction in the total melt derived from antarctica and a refinement of the 1 kyr temporal resolution assumed in the construction of the theoretical solution

influence of inherited geologic framework on barrier shoreface morphology and dynamics abstract passive margin coastlines with limited sand supplies such as much of the u s atlantic margin are significantly influenced by the geologic framework of older stratigraphic units that occur beneath and seaward of the shoreface many u s east coast barrier islands are perched barriers in which the underlying pre modern sediments determine the morphology of the shoreface and strongly influence modern beach dynamics and composition perched barriers consist of varible layers of beach sand on top of older eroding stratigraphic units with highly variable compositions and geometries along many parts of the coastal system stratigraphically controlled bathymetric features on the inner shelf modify waves and currents and thereby effect patterns of sediment erosion transport and deposition on the adjacent shoreface it is essential to understand this geologic framework before attempting to model the large scale behavior of these types of coastal systems in north carolina most shoreline features are controlled by the pre holocene stratigraphic framework of the shoreface the beaches are perched on top of pre existing pleistocene tertiary and cretaceous sediments the surficial geology of the coastal zone is subdivided into two distinct provinces resulting in different stratigraphic controls of the shoreface north of cape lookout the geological framework consists of a quaternary sequence that fills a regional depositional basin called the albemarle embayment the coastal zone south of cape lookout is dominated by tertiary and cretaceous units that crop out across the coastal plain and continental shelf with very thin quaternary units only locally preserved superimposed upon this regional stratigraphy is an ancient drainage system resulting in a series of fluvial valleys filled with younger coastal sediments separated by large interfluve areas of older stratigraphic units this results in a coastal system in which the shoreface is either nonheadland or headland dominated respectively headland dominated shorefaces are further divided into subaerial and submarine categories nonheadland dominated shorefaces are further divided into those influenced primarily by transgressive or regressive processes or channel dominated depositional processes i e inlet migration or stream valley fill examples of each of these six types of shorefaces are presented to demonstrate the control that the geologic framework exhibits on shoreface morphologies and processes

uranium series coral ages from the us atlantic coastal plain the 80 ka problem revisited abstract uranium series coral ages for emergent units from the passive continental margin us atlantic coastal plain acp suggest sea level above present levels at the end of marine oxygen isotope stage mis 5 contradicting age elevation relations based on marine isotopic or coral reef models of ice equivalent sea level we have reexamined this problem by obtaining high precision 230th 238u and 231pa 235u thermal ionization mass spectrometric ages for recently collected and carefully cleaned acp corals many in situ we recognize samples that show no evidence for diagenesis on the basis of uranium isotopic composition and age concordance combining new and earlier data among those ages close to or within the age range of mis 5 over 85 cluster between 65 and 85 ka bp of the corals that we have analyzed those that show the least evidence for diagenesis on the basis of uranium isotopic composition and age concordance have ages between 80 and 85 ka bp consistent with a mis 5a correlation the units from which these samples have been collected are all emergent and have elevations within 3 5 m of those few units where early stage 5 125 000 ka bp coral ages have been obtained the acp appears to record an unusual history of relative sea level throughout mis 5 a history that is also apparent in the dated coral record for bermuda we speculate that this history is related to the regional near to intermediate field effects of ancestral laurentide ice sheets on last interglacial shorelines of the western north atlantic

sea level changes since the last glacial maximum an appraisal of the ipcc fourth assessment report the ipcc fourth assessment report ar4 stated that global sea level rose by about 120 m between the last glacial maximum lgm and 3 2 ka and did not rise again until the late 19th century a review of relevant literature demonstrates that the rise may have been larger by 10 15 m that the timing of stabilisation is poorly constrained within the last 7 ka bp and that the onset of modern rates of sea level rise is not synchronous and uniform across the globe the lgm lowstand as defined in the ar4 is based on the classic barbados sea level history but the sea level curve from this island may not be an accurate eustatic approximation if glacial isostatic adjustment gia processes were significant as suggested by various authors the barbados sea level curve revealed the existence of meltwater pulse mwp 1a at around 14 000 cal a bp questions about the source and causal mechanism of mwp 1a are still being explored by field scientists and gia modellers these problems have direct relevance for contemporary measurements of ice mass changes because space geodetic measurements rely on information provided by gia models to separate land motion from ice mass changes global patterns of holocene sea level change are controlled by regional sea level variability not only through isostatic and tectonic processes but also through steric effects longer wavelength gravitational changes produced by changing ice ocean mass flux and hemispheric scale perturbations in the earth s rotation eustasy is therefore merely a concept not a measurable quantity constraining the late holocene ice melt contribution to global sea level rise and determining regional sea level rise patterns in the 18th and 19th centuries are important future tasks for sea level scientists these will establish the baseline contributions to 20th and 21st century sea level rise and will help to determine the causes of modern rates of sea level rise constraining historical sea level accelerations and short term ice mass flux will aid models of ice sheet dynamics and help to reduce current uncertainties in future sea level predictions the ar4 shows that regional sea level variability is clearly present in sea level change patterns for the past 50 a and an important challenge for the next ipcc assessment is to incorporate this variability into regional future sea level rise scenarios copyright 2009 john wiley sons ltd

gulf stream shifts following enso events over the past three decades the annual mean latitude of the gulf stream off the coast of the united states has been forecastable from the intensity of the north atlantic oscillation nao 1 the predictions accounting for more than half the variance here we show that much of the unexplained variance can be accounted for by the southern oscillation in the pacific the gulf stream being displaced northwards following el nino southern oscillation enso events this provides a link between events in the equatorial pacific and the circulation and weather conditions of the north atlantic

ice volume and sea level during the last interglacial during the last interglacial period 125 000 years ago sea level was at least several meters higher than at present with substantial variability observed for peak sea level at geographically diverse sites speculation that the west antarctic ice sheet collapsed during the last interglacial period has drawn particular interest to understanding climate and ice sheet dynamics during this time interval we provide an internally consistent database of coral u th ages to assess last interglacial sea level observations in the context of isostatic modeling and stratigraphic evidence these data indicate that global eustatic sea level peaked 5 5 to 9 meters above present sea level requiring smaller ice sheets in both greenland and antarctica relative to today and indicating strong sea level sensitivity to small changes in radiative forcing

quaternary climates and sea levels of the u s atlantic coastal plain uranium series dating of corals from marine deposits of the u s atlantic coastal plain coupled with paleoclimatic reconstructions based on ostracode marine and pollen continent data document at least five relatively warm intervals during the last 500 000 years on the basis of multiple paleoenvironmental criteria we determined relative sea level positions during the warm intervals relative to present mean sea level were 7 5 meters at 188 000 years ago 7 5 1 5 meters at 120 000 years ago 6 5 3 5 meters at 94 000 years ago and 7 3 meters at 72 000 years ago the composite sea level chronology for the atlantic coastal plain is inconsistent with independent estimates of eustatic sea level positions during interglacial intervals of the last 200 000 years hydroisostatic adjustment from glacial interglacial sea level fluctuations lithospheric flexure and isostatic uplift from sediment unloading due to erosion provide possible mechanisms to account for the discrepancies alternatively current eustatic sea level estimates for the middle and late quaternary may require revision

deglacial meltwater pulse 1b and younger dryas sea levels revisited with boreholes at tahiti reconstructing sea level changes during the last deglaciation provides a way of understanding the ice dynamics that can perturb large continental ice sheets the resolution of the few sea level records covering the critical time interval between 14 000 and 9 000 calendar years before the present is still insufficient to draw conclusions about sea level changes associated with the younger dryas cold event and the meltwater pulse 1b mwp 1b we used the uranium thorium method to date shallow living corals from three new cores drilled onshore in the tahiti barrier reef no significant discontinuity can be detected in the sea level rise during the mwp 1b period the new tahiti sea level record shows that the sea level rise slowed down during the younger dryas before accelerating again during the holocene

ice 3g a new global model of late pleistocene deglaciation based upon geophysical predictions of post glacial relative sea level change a new high resolution global model of late pleistocene deglaciation is inferred on the basis of geophysical predictions of postglacial relative sea level variations in which the ice ocean solid earth interaction is treated in a gravitationally self consistent fashion for the purpose of these analyses the radial viscoelastic structure of the planet is assumed known on the basis of previously published sensitivity tests on solutions of the forward problem only radiocarbon controlled relative sea level histories from sites that were actually ice covered with one or two additions are employed to constrain the model leaving relative sea level rsl data from sites that were not ice covered to be employed to confirm its consistency results for these confirmatory analyses are reported elsewhere here the new deglaciation model referred to as ice 3g is compared to previous models derived by several independent means and tested against a number of additional observations other than sea level histories including geologically controlled retreat isochrones oxygen isotope data from deep sea sedimentary cores and coral terrace elevations the latter two observations strongly constrain the net sea level rise that has occurred since the onset of deglaciation and therefore the mass of ice that melted during the last glacial interglacial transition

refining the eustatic sea level curve since the last glacial maximum using far and intermediate field sites the eustatic component of relative sea level change provides a measure of the amount of ice transferred between the continents and oceans during glacial cycles this has been quantified for the period since the last glacial maximum by correcting observed sea level change for the glacio hydro isostatic contributions using realistic ice distribution and earth models during the last glacial maximum lgm the eustatic sea level was 125 5 m lower than the present day equivalent to a land based ice volume of 4 6 4 9 107 km3 evidence for a non uniform rise in eustatic sea level from the lgm to the end of the deglaciation is examined the initial rate of rise from ca 21 to 17 ka was relatively slow with an average rate of ca 6 m ka 1 followed by an average rate of ca 10 m ka 1 for the next 10 ka significant departures from these average rates may have occurred at the time of the younger dryas and possibly also around 14 ka most of the decay of the large ice sheets was completed by 7 ka but 3 5 m of water has been added to the oceans since that time

shallow cenozoic seismic stratigraphy and structure south carolina lower coastal plain and continental shelf single channel high resolution seismic reflection data from the south carolina lower coastal plain and continental shelf delineate no substantial deformation that could possibly be associated with the seismicity of the charleston area correlation of the seismic data with available wells reveals seaward dipping paleocene through quaternary depositional sequences representing carbonate and terrigenous sediments that were deposited in shallow to outer shelf paleoenvironments only middle eocene and younger units are delineated on the lower coastal plain due to limited acoustic penetration the seismic profiles also reveal thick miocene and pliocene progradational sediments within a broad north northwest south southeast trending depositional basin in the middle to outer shelf region the variations in the thicknesses of the depocenters are attributed to an interrelationship of subaerial and marine processes which are in turn governed by the shifting of the gulf stream the suwannee channel and sea level the cenozoic section in the study area indicates a stable structural framework except offshore charleston where the paleocene through miocene reflectors are displaced by a northeast southwest trending monoclinal flexure downthrown to the southeast the amount of displacement decreases from 20 m on the paleocene surface to 10 m on the shallowest miocene reflector seen 10 m below the sea floor this flexure probably originated by reactivation of the deeply seated pre cretaceous helena banks fault revealed in multichannel profiles reported elsewhere

holocene sea level variation and spit development data from skagen odde denmark extensivxe exposures of peat located in initer ridge swales at the contact between beach anid oxerlyiing coastal dune deposits at skagen odde northern denmark provide a record of spit development in relation to glacioisostatic rebound and sea level variation the elevationi of the base of the swale peats was measured over a distanlce of l5 kmni anid rcpresenits spit gosowth bet necen 6000 and 1400 cal veairs bp tlle swale pealts fall from 13 14 m a s l in the south proximiial part to 3 4 m a s l in the north distal part reflecting the inifluenice of ostatic rebounid diting spit gtowsth the nesw data suggest that isostatic rebound progressively declined with time fromi c 3 mm yr to c 1 5 mm yr superimposed on the isostatic controlled changes are smaller scale fluctations in peat elevation related to eustatic sea level changes sea level higlhstands ae iden1 t ified at 5450 2 7 in 4700 1 7 m and 2450 cal years bp 0 4 m anid lowstands at 5200 1 5 m 4100 1 9 mn anid 1650i

mid holocene emergence of southern tunisian coasts abstract we present new sea level data from the coasts of southern tunisia between the gulf of gabes and the libyan border the work tests previously published evidence on holocene shorelines and confirmed that a distinct emergence has occurred in this area during this time the emergence peak lies at least 186 11 cm above present and is inferred from 1 ams radiocarbon dates of subtidal vermetids and boring shells collected in growth position and 2 careful assessment of tidal heights maximum emergence took place between about 6000 and 5000 14c years bp it cannot be ascribed to tectonics and is probably related to post glacial hydro isostatic effects it challenges the inference of a 3 m global sea level rise since 6000 years bp due to residual antarctic melting

flow characteristics within different configurations of submerged flexible vegetation summary the effects of three configurations aligned staggered and columnar of submerged flexible vegetation on flow structure are investigated experimentally in the laboratory time averaged flow velocity and turbulence behavior are evaluated at different positions in each configuration by using a 3d acoustic doppler velocimeter adv according to the hydrodynamic regimes in experimental results the vertical distribution of streamwise velocity can be separated into three layers the upper non vegetated layer middle vegetation layer and lower sheath layer this three layer model which is associated with different logarithmic equations can be applied to describe the vertical distribution of streamwise velocity the local maximum velocity within vegetation occurs at the sheath section of a plant clump 0 10 0 15 vegetation height h v where the frontal width is minimal turbulent intensities in the streamwise u rms and spanwise v rms directions peak at the sheath section and at the approximate top of the canopy 0 9 1 2 h v the maximum reynolds stresses exist at roughly 0 9 1 2 h v which may be migrated vertically as the frontal width of a plant clump is increased this high frontal width also increases streamwise velocity above vegetation leading to increase variations in reynolds stresses around the canopy top on the vertical turbulent velocity scale w rms the vortices above a still canopy rotate faster than those above a waving canopy therefore the experimental results demonstrate that the flow field can vary significantly at the sheath section and at the top of a plant clump due to altered flow pass these analytical findings will likely prove useful when designing ecological habitats and preventing riverbed erosion

anatomy and sedimentary model of a hooked spit sylt southern north sea a sedimentary model for hooked spit depositional systems based on ground penetrating radar and sedimentological data is presented the recurved main spit of sylt island southern north sea is dominated by migrating sand dunes the investigated hooked spit exhibits a system of foredune ridges oriented perpendicular to the dunes of the recurved spit the development of the hooked spit is related closely to the presence of an adjacent tidal inlet where strong tidal currents and a steep bathymetry prevent a further northward progradation of the main spit and trigger a deflection from northerly directed to easterly directed net sediment transport ground penetrating radar data and shallow sediment cores reveal the sedimentary architecture of the hooked spit in high resolution and allow the proposition of a genetic stratigraphic model it is shown that the growth of the hooked spit is controlled by the interplay of alongshore migrating foreshore beach drifts under fair weather conditions and strong erosional events interpreted as the result of rare severe storms these storms may excavate scarps in the backshore which play an important role in the development of foredune ridges accelerator mass spectrometry 14c ages indicate an absolute age of at least 1300 years for the hooked spit which possibly correlates with strengthened erosion of the main spit in contrast to the main spit where the sediment budget is negative nowadays growth of the hooked spit beach accelerated significantly during the last decades this effect can probably be attributed to enhanced beach nourishments updrift along the main spit and makes the investigated hooked spit a natural laboratory to study the influence of increasing sediment supply into a system developing under the conditions of sea level rise the study shows that the same external forces lead to distinct progradational processes along one barrier spit system

spectral wave flow attenuation within submerged canopies implications for wave energy dissipation 1 communities of benthic organisms can form very rough surfaces canopies on the seafloor previous studies have shown that an oscillatory flow induced by monochromatic surface waves will drive more flow inside a canopy than a comparable unidirectional current this paper builds on these previous studies by investigating how wave energy is attenuated within canopies under spectral wave conditions or random wave fields defined by many frequencies a theoretical model is first developed to predict how flow attenuation within a canopy varies among the different wave components and predicts that shorter period components will generally be more effective at driving flow within a canopy than longer period components to investigate the model performance a field experiment was conducted on a shallow reef flat in which flow was measured both inside and above a model canopy array results confirm that longer period components in the spectrum are significantly more attenuated than shorter period components in good agreement with the model prediction this paper concludes by showing that the rate at which wave energy is dissipated by a canopy is closely linked to the flow structure within the canopy under spectral wave conditions wave energy within a model canopy array is dissipated at a greater rate among the shorter period wave components these observations are consistent with previous observations of how wave energy is dissipated by the bottom roughness of a coral reef

nature based flood protection the efficiency of vegetated foreshores for reducing wave loads on coastal dikes this paper analyses the effect of vegetation on wave damping under severe storm conditions based on a combination of field measurements and numerical modelling the field measurements of wave attenuation by vegetation were performed on two salt marshes with two representative but contrasting coastal wetland vegetation types cordgrass spartina anglica and grassweed scirpus maritimus the former is found in salty environments whereas the latter is found in brackish environments the measurements have added to the range with the highest water depths and wave heights presented in the literature so far a numerical wave model swan has been calibrated and validated using the new field data it appeared that the model was well capable of reproducing the observed decay in wave height over the salt marsh the model has been applied to compute the reduction of the incident wave height on a dike for various realistic foreshore configurations and hydraulic loading conditions additionally the efficiency of vegetated foreshores in reducing wave loads on the dike has been investigated where wave loads were quantified using a computed wave run up height and wave overtopping discharge the outcomes show that vegetated foreshores reduce wave loads on coastal dikes significantly also for the large inundation depths that occur during storms and with the vegetation being in winter state the effect of the foreshore on the wave loads varies with wave height to water depth ratio on the foreshore the presence of vegetation on the foreshore extends the range of water depths for which a foreshore can be applied for effective reduction of wave loads and prevents intense wave breaking on the foreshore to occur this research demonstrates that vegetated foreshores can be considered as a promising supplement to conventional engineering methods for dike reinforcement

flow and deposition in and around a finite patch of vegetation this laboratory study describes the flow and deposition observed in and around a finite patch of vegetation located at the wall of a channel two patch densities are considered with 2 and 10 solid volume fraction the velocity field measured in and around the patch by acoustic doppler velocimetry revealed three distinct zones first there is a diverging flow region at the leading edge of the patch where the flow in line with the patch decelerates and the bulk of the flow is diverted toward the open channel second there is a fully developed region within the vegetation where the velocity is uniform across the patch width and along the length of the patch third a shear layer forms at the interface between the patch and adjacent open channel the pattern of deposition in and around the vegetation was characterized by releasing 12 micron spherical glass particles and recording net deposition on a set of glass slides in the diverging region net deposition increases in the stream wise direction as the local velocity decreases in the fully developed region of the patch deposition decreases with longitudinal position as the concentration in the water column is depleted the deposition pattern is nearly uniform across the patch width consistent with the velocity field and suggesting that turbulent diffusive flux across the lateral edge of the patch is not a significant source of particles to the patch under the conditions studied here

hydrodynamics of model posidonia oceanica patches in shallow water the hydrodynamics of simulated patches of the mediterranean seagrass posidonia oceanica were studied in laboratory flume experiments in which the height of the pronated canopy was always greater than half the total water depth the effects of variations in speed from 0 08 m s 21 to 0 24 m s 21 and patch configuration on the hydrodynamics were investigated significant speeds penetrated the patches to approximately half their height reducing speed did not change the flow patterns observed except to weaken and blur them flow encountering a single patch formed a turbulent wake at the height of the top of the canopy within this wake the vertical shear stress decreased monotonically downstream but the reynolds stress increased initially and then decayed when a second patch was positioned within the region where reynolds stress increased referred to as the 06 patch the wake center penetrated it causing average turbulent velocities with horizontal components 3 3 times higher and vertical components 4 2 times higher than in the upstream patch when this patch was positioned where the reynolds stress decayed referred to as the 14 patch the wake center rose above it nevertheless the turbulence in the 14 patch had horizontal components 12 higher and vertical components 22 higher on average than in the 06 patch because its upstream end was closer to the reynolds stress maximum thus the ratio of the patch separation to the length of wake in which the reynolds stress increased was identified as central to quantifying the turbulence within the downstream patch the increased turbulence is likely to be important in determining sedimentary and ecological patch characteristics by increasing retention of particulates in suspension and thus reducing depositional rates of for example larvae nutrients and dead organic matter

the role of hydrodynamic forcing sediment transport processes and bottom substratum in the shoreward development of posidonia oceanica meadow abstract this paper investigates the combined role of hydrodynamic forcing sediment transport processes and sea bottom features in determining the location of the meadow upper limit of the endemic mediterranean seagrass posidonia oceanica for this purpose an approach including extreme wave analysis and numerical modelling is applied to two sandy beach systems located in southern sardinia italy information about bathymetry p oceanica meadow extension and bottom features has been made available by previous published studies based on the 30 year long noaa hindcast dataset a wave climate analysis is carried out to identify the incoming storm wave conditions 1 year return period to be simulated with the delft3d model package the simulation results extend the current knowledge highlighting the importance of wave induced hydrodynamic parameters as limiting factors for the survival of p oceanica meadows in particular the results suggest that on sandy substrata the meadow upper limit lies well offshore of the surf zone in areas with little morphological activity where the wave orbital velocities associated to storms are on the order of 0 8 m s and the mean current magnitude does not exceed 0 5 m s on rocky bottoms the p oceanica meadow can extend up to the outer surf zone of storms and is thus able to colonize shallow areas subject to stronger hydrodynamic forcings than those observed on sand this difference in the plant tolerance to wave forcing depending on the substratum type shows how both hydrodynamic and geological factors play a key role in defining the environmental conditions for the development of seagrass meadows

timing of the last glacial maximum from observed sea level minima during the last glacial maximum ice sheets covered large areas in northern latitudes and global temperatures were significantly lower than today but few direct estimates exist of the volume of the ice sheets or the timing and rates of change during their advance and retreat here we analyze four distinct sediment facies in the shallow tectonically stable bonaparte gulf australia each of which is characteristic of a distinct range in sea level to estimate the maximum volume of land based ice during the last glaciation and the timing of the initial melting phase we use faunal assemblages and preservation status of the sediments to distinguish open marine shallow marine marginal marine and brackish conditions and estimate the timing and the mass of the ice sheets using radiocarbon dating and glacio hydroisostatic modelling our results indicate that from at least 22 000 to 19 000 calendar years before present land based ice volume was at its maximum exceeding today s grounded ice sheets by 52 5 x 10 exp 6 cu km a rapid decrease in ice volume by about 10 percent within a few hundred years terminated the last glacial maximum at 19 000 250 years

evidence for massive discharges of icebergs into the north atlantic ocean during the last glacial period sediments in the north atlantic ocean contain a series of layers that are rich in ice rafted debris and unusually poor in foraminifera1 here we present evidence that the most recent six of these heinrich layers deposited between 14 000 and 70 000 years ago record marked decreases in sea surface temperature and salinity decreases in the flux of planktonic foraminifera to the sediments and short lived massive discharges of icebergs originating in eastern canada the path of the icebergs clearly marked by the presence of ice rafted detrital carbonate can be traced for more than 3 000 km a remarkable distance attesting to extreme cooling of surface waters and enormous amounts of drifting ice the cause of these extreme events is puzzling they may reflect repeated rapid advances of the laurentide ice sheet perhaps associated with reductions in air temperatures yet temperature records from greenland ice cores appear to exhibit only a weak corresponding signal moreover the 5 10 000 yr intervals between the events are inconsistent with milankovitch orbital periodicities raising the question of what the ultimate cause of the postulated cooling may have been

mixing layers and coherent structures in vegetated aquatic flows 1 to date flow through submerged aquatic vegetation has largely been viewed as perturbed boundary layer flow with vegetative drag treated as an extension of bed drag however recent studies of terrestrial canopies demonstrate that the flow structure within and just above an unconfined canopy more strongly resembles a mixing layer than a boundary layer this paper presents laboratory measurements obtained from a scaled seagrass model that demonstrate the applicability of the mixing layer analogy to aquatic systems specifically all vertical profiles of mean velocity contained an inflection point which makes the flow susceptible to kelvin helmholtz instability this instability leads to the generation of large coherent vortices within the mixing layer observed in the model at frequencies between 0 01 and 0 11 hz which dominate the vertical transport of momentum through the layer the downstream advection of these vortices is shown to cause the progressive coherent waving of aquatic vegetation known as the monami when the monami is present the turbulent vertical transport of momentum is enhanced with turbulent stresses penetrating an additional 30 of the plant height into the canopy

the influence of waves and seagrass communities on suspended particulates in an estuarine embayment resuspension of bottom sediments by waves corresponding changes in suspended particulate material spm concentrations in the overlying water column and transport pathways of spm were investigated in a shallow estuarine embayment colonized by seagrass communities in chesapeake bay in shallow 2 m unvegetated regions significant resuspension of bottom sediments was evident when northerly winds exceeded 25 km h 1 increasing spm concentrations up to 10 fold high concentrations of spm generated by resuspension dissipated rapidly within 24 h after winds became calm patterns of spm along the embayment s depth gradient suggest that part of this resuspended material was transported offshore into deeper reaches of the estuary in areas of the embayment colonized by seagrasses wave energy was attenuated by the vegetation suppressing resuspension and enhancing deposition as a result spm concentrations were significantly lower inside seagrass beds than in adjacent unvegetated areas during periods of high winds when wave induced resuspension occurred in unvegetated areas spm concentrations remained unchanged inside the bed at normal water levels however when water levels were elevated by spring tides or storm surges plants were less effective at attenuating wave energy and spm concentrations increased inside the seagrass bed due to resuspension and advective processes calculations based on the results of this study indicate that sedimentation rates are substantially higher in seagrass communities than in unvegetated areas

luminescence dating of holocene sedimentary deposits on romo a barrier island in the wadden sea denmark this study presents an optically stimulated luminescence osl based chronology for the evolution of the barrier island romo and related back barrier lagoon deposits in the danish wadden sea the chronology is constructed using 78 quartz osl ages obtained using a single aliquot regenerative dose sar protocol samples were retrieved from seven sediment cores each up to 25 m long taken from locations on the island and within the back barrier lagoon the reliability of the osl results is assessed using preheat plateaus thermal transfer tests and dose recovery measurements and by comparison with independent age control the osl ages compare favourably with three 14c age estimates and range between 220 20 and 15 800 1200 years romo appears to have developed as a progradational barrier system and the island appeared for the first time approximately 8000 years ago it then gradually expanded towards the west north and south as a result of an abundant sediment supply luminescence dating is concluded t