sea cliffs their processes profiles and classification general concavity or convexity of sea cliff profiles is controlled by relative rates of erosion by marine and subaerial processes as well as by positions of more resistant strata in the cliffs profiles supplemented by on site examination can establish the activity and dominance of erosional processes and indicate changes in regimen a sharp angle at the sea cliff base generally indicates active marine erosion whereas a smooth curve at the base means that subaerial erosion may dominate talus shows absence of marine erosion studies of profiles can be useful for estimating stability for residences railroads and highways at the top face and base of sea cliffs generally increased erosion and retreat of sea cliffs are in prospect because of projected regionally wetter and stormier climate rising sea level and increased human activities

sea cliff erosion as a function of beach changes and extreme wave runup during the 1997 1998 el nino abstract over time scales of hundreds to thousands of years the net longshore sand transport direction along the central california coast has been driven to the south by north pacific winter swell in contrast during the el nino winter of 1997 1998 comparisons of before and after airborne lidar surveys showed sand was transported from south to north and accumulated on the south sides of resistant headlands bordering pocket beaches this resulted in significant beach erosion at the south ends of pocket beaches and deposition in the north ends coincident with the south to north redistribution of sand shoreline morphology became prominently cuspate with longshore wavelengths of 400 700 m the width and elevation of beaches were least where maximum shoreline erosion occurred preferentially exposing cliffs to wave attack the resulting erosional hotspots typically were located in the embayments of giant cusps in the southern end of the pocket beaches the observed magnitude of sea cliff retreat which reached 14 m varied with the number of hours that extreme wave runup exceeded certain thresholds representing the protective capacity of the beach during the el nino winter a threshold representing the width of the beach performed better than a threshold representing the elevation of the beach the magnitude of cliff erosion can be scaled using a simple model based on the cross shore distance that extreme wave runup exceeded the pre winter cliff position cliff erosion appears to be a balance between terrestrial mass wasting processes which tend to decrease the cliff slope and wave attack which removes debris and erodes the cliff base increasing the cliff slope

an exploratory numerical model of rocky shore profile evolution abstract rocky shores occur along much of the world s coastline and include a wide range of coastal morphologies such as intertidal shore platforms considerable research effort has been placed on trying to understand developmental processes on rocky shores but progress has been forestalled because these landscapes develop slowly and preserve little evidence of evolution through time this paper presents a new exploratory numerical model developed to study long term shore profile evolution on rock coasts the model purposely considers only a limited number of processes each represented in a highly abstracted way despite these simplifications the model exhibits a large range of emergent shore profile shapes this behavior is enabled both by broader spatial representation of the driving erosion forces and the flexibility provided by a grid discretization scheme initial model testing shows the development of varied rocky profile geometries ranging from steep plunging cliffs cliffs with narrow benches and cliffs with a variety of shore platform shapes most of the model geometries are similar to those observed in the field and model behavior is robust and internally consistent across a relatively large parameter space this paper provides a detailed description of the new model and its subsequent testing emphasis is placed on comparison of model results with published field observations in which morphometric relationships are described between shore platform gradient and tidal range and platform elevation and platform width the model adequately simulates these morphometric relationships while retaining its ability to simulate a wide range of profile shapes the simplicity of process representations and the limited number of processes implemented means that model outputs can be interpreted reasonably easily hence an opportunity is now provided following the testing described in this paper to use the model to systematically investigate the broader controlling conditions on rock shore profile development

identifying the behavioural characteristics of clay cliffs using intensive monitoring and geotechnical numerical modelling abstract coastal monitoring is routinely undertaken to provide an archival record of cliff line movement that can be used in the development and validation of predictive coast retreat and evolution models however coastal monitoring is often purely quantitative in nature and financial necessity requires deployment over extensive coastal sections as a result for local site conditions in particular only limited geomorphological data are available or included during the development of such predictive models this has resulted in many current models incorporating a simplistic or generalised representation of cliff behaviour an approach that progressively loses local credibility when deployed over extensive heterogeneous coastlines this study addresses this situation at a site of extreme coastline retreat holderness uk through the application of intensive monitoring of six representative cliff sections nested within a general geomorphological appraisal of the wider coastline as a whole the data from these surveys have been used to validate a finite difference based geotechnical modelling assessment of clay cliff stability once validated the geotechnical model was used to simulate a range of scenarios that were sufficient to represent the range of topographic hydrogeological geological and littoral conditions exhibited throughout the region our assessment identified that the cliff retreat occurs through the combined influence of direct marine erosion of the cliff with shallow structurally controlled failures or substantial mass failures critically the predisposition to any one of these failure mechanisms arises principally as a result of initial cliff height the results of the numerical modelling have been combined into an empirical slope model that derives the rate of landslide induced retreat that would arise from mass failures under various future scenarios results of this study can be used in the selection and development of retreat models at coastlines of similar physiographic setting to that found at holderness the results represent a key step in linking material deformation properties to the processes of cliff change and the subsequent range of landforms found on clay cliffs as such the results could also be used more generally to illustrate the likely cliff behaviour of other soft rock coastlines

coastal cliff behaviour observations on the relationship between beach levels and recession rates abstract beaches dissipate wave energy and regulate the frequency that the cliff foot is subject to wave attack the relationship between beach levels and cliff recession rates has been established for pleistocene soft rock cliffs along the north norfolk and suffolk coasts uk the results suggest that over a decadal timescale there is a non linear increase in the average recession rate as the beach profile area above high water mark hwm decreases small changes in beach level can result in significant differences in the recession rates the impact of a unit change in beach level on the recession rate depends on the initial beach level on a year by year basis it is possible to divide the beach level and recession relationship into a series of zones with characteristic types of behaviour at low beach levels there is high to extremely high recession with considerable variability whereas at high beach levels there is almost zero recession with limited variability it is concluded that historical recession rates are the product of both the past forcing events and changes in cliff beach state extrapolation of historical rates can be extremely unreliable unless it is supported by an understanding of the dynamic behaviour of the cliff beach system and the energy inputs over the observation period

thick bottom nepheloid layers in the western mediterranean generated by deep dense shelf water cascading the analysis of a compilation of deep ctd casts conducted in the western mediterranean from 1998 to 2011 has documented the role that dense water formation and particularly deep dense shelf water cascading off the gulf of lions plays in transporting suspended particulate matter from the coastal regions down to the basin deep ctd casts reveal that after the 1999 and 2005 2006 deep cascading events the western mediterranean deep water wmdw was characterized by the presence of a thick bottom nepheloid layer bnl that corresponded in thickness with a thermohaline anomaly generated by the mixture of dense waters formed by deep convection in the open sea and by deep cascading this bnl can be hundreds of meters thick and in the central part of the basin usually exhibits suspended sediment concentrations of 1 mg l after winter 1999 the bnl spread from the gulf of lions and the catalan margin over the northwestern mediterranean basin reaching west of the balearic islands and the ligurian sea while after winters 2005 2006 the bnl covered the entire western mediterranean basin thickness and concentration of the bnl tend to diminish with time but this trend is highly dependent on the volume of dense water generated both by convection and cascading after winter 1999 the bnl signal vanished in one year but after winters 2005 2006 it lasted for longer and the turbidity signal can still be distinguished at present 2011 particle size distribution in the bnl reveals the presence of large aggregates up to 1 mm in size formed by a mixture of single particles with the same bimodal grain size distribution as the surface sediments found in the northwestern mediterranean slope and basin results presented in this paper highlight the fact that the wmdw can be periodically affected by the arrival of new dense waters loaded with suspended particles mainly introduced by resuspension processes during major cascading events being a key process that could ultimately affect deep sea biogeochemical cycles in the western mediterranean

post eruptive morphological evolution of island volcanoes surtsey as a modern case study abstract surtsey is a small volcanic island in the vestmannaeyjar archipelago off the south coast of iceland the eruption leading to the island s emersion lasted for 3 5 yr 1963 1967 while destructive forces have been active for over 50 yr 1963 present day during which surtsey has suffered rapid subaerial and submarine erosion and undergone major morphological changes surtsey is a well documented modern example of the post eruptive degradational stage of island volcanoes and has provided the unique opportunity to continuously observe and quantify the effects of intense geomorphic processes in this paper we focus on coastal and marine processes re shaping the shoreline and shallow water portions of the surtsey complex since its formation and on the related geomorphological record analogies with the post eruptive morphological evolution of recently active island volcanoes at the emerging stage encompassing different climatic conditions wave regimes and geological contexts are discussed

particle fluxes induced by benthic storms during the 2012 dense shelf water cascading and open sea convection period in the northwestern mediterranean basin abstract the effects of deep dense shelf water cascading and open sea convection on the sediment dynamics of the northwestern mediterranean basin were studied by near bottom moored instruments recording trapped particle fluxes suspended particle fluxes water properties and hydrodynamics from november 2011 to july 2012 during this period near bottom currents induced by winter dense water formation generated benthic storms that caused resuspension at 2450 m water depth increasing by more than one order of magnitude the ambient suspended sediment concentrations the trapped particle fluxes and the suspended sediment fluxes during the preconditioning phase of the open sea convection from december 2011 to mid february 2012 currents 1 10 cm s 1 suspended sediment concentrations

stochastic simulation of episodic soft coastal cliff recession probabilistic methods provide a means of demonstrating the potential variability in predictions of coastal cliff recession they form the basis for risk based land use planning cliff management and engineering decision making a range of probabilistic methods for predicting soft coastal cliff recession has now been developed including statistical techniques process based simulation and structured use of expert judgement a new episodic stochastic simulation model is introduced which models the duration between cliff falls as a gamma process and fall size as a log normal distribution the method is applied to cliff recession data from a coastal site in the uk using maximum likelihood and bayesian parameter estimation techniques the bayesian parameter estimation method enables expert geomorphological assessment of the local landslide characteristics and measurements of individual cliff falls to be combined with sparse historic records of cliff recession an episodic simulation model is often preferable to conventional regression models which are based on assumptions that are seldom consistent with the physical process of cliff recession

a new process response coastal recession model of soft rock cliffs abstract the development of cliff erosion predictive models is limited by the complex interactions between environmental processes and material properties over a range of temporal and spatial scales current models incorporate a stochastic representation of cliff behavior based on assumptions regarding the magnitude and frequency of events in a probabilistic framework the new model presented here has been developed to incorporate the behavioral and mechanical characteristics of coastal cliffs which are dominated geologically by overconsolidated clays tills and an associated protective colluvial wedge this model is capable of providing precise and stable responses to some of the inherent uncertainties in cliff recession processes including those caused by different failure mechanisms e g colluvium generation groundwater and erosive tidal cycles material strength is incorporated using the unconfined compressive strength of the material that composes the cliff unlike previous models a calibration parameter is restricted to account for uncertainties linked to marine processes the mechanisms of cliffline retreat have been identified as slump and topple landslides once cliff material has fallen colluvium formation at the cliff foot is incorporated into the model using three different procedures according to the geomechanical characteristics of the debris the model is validated through profile evolution assessment at various locations of coastline retreat on the holderness coast uk higher groundwater content also produces an increase in the number and size of the slope failures the results represent an important step forward in linking material properties to the processes of cliff recession

lithological controls on soft cliff planshape evolution under high and low sediment availability this paper addresses a series of geomorphic questions relating to large scale 1 km long term 100 1 000 years coastal planshape evolution previous research on soft cliff coasts has recognised the role of protective fronting beach volumes on reducing rates of cliff toe retreat however it is the maintenance of this critical threshold that ultimately determines two contrasting modes of shoreline behaviour mode a in which there is little beach sediment and shoreline evolution is controlled by material strength and mode b when ample beach sediment means that shoreline evolution is controlled by longshore sediment transport here we use a numerical model scape to investigate temporal and spatial changes in beach volume on a broader range of feedbacks than considered in previous models the transition between mode a and mode b coasts is defined by relative sediment inputs to outputs and used to explore how these contrasting modes control the evolution of an initial linear frontage exhibiting longshore changes in cliff lithology material resistance and the proportion of beach grade material in the eroded bedrock under mode a relative changes in material resistance result in long term heterogeneous rates of retreat which result in the development of persistent headland and embayment features however under mode b feedbacks between coastal planshape longshore sediment transport beach volume and wave energy result in steady state retreat rates regardless of longshore variations in resistance results are compared and contrasted to previous simulations and site specific examples and a conceptual model of mode a and mode b interactions presented copyright 2015 john wiley sons ltd

dynamic jamming of iceberg choked fjords we investigate the dynamics of ice melange by analyzing rapid motion recorded by a time lapse camera and terrestrial radar during several calving events that occurred at jakobshavn isbrae greenland during calving events 1 the kinetic energy of the ice melange is 2 orders of magnitude smaller than the total energy released during the events 2 a jamming front propagates through the ice melange at a rate that is an order of magnitude faster than the motion of individual icebergs 3 the ice melange undergoes initial compaction followed by slow relaxation and extension and 4 motion of the ice melange gradually decays before coming to an abrupt halt these observations indicate that the ice melange experiences widespread jamming during calving events and is always close to being in a jammed state during periods of terminus quiescence we therefore suspect that local jamming influences longer timescale ice melange dynamics and stress transmission

jakobshavns glacier drainage basin a balance assessment maximum and minimum estimates are made of the drainage basin feeding the jakobshavns glacier by using surface elevation maps derived from seasat altimetry benson s 1962 net balance measurements are used to calculate the balance flow within the basin comparisons of the balance flux at the terminus with estimates of actual flux suggest the basin is in overall equilibrium or slightly thickening this agrees with measurements along the nearby egig traverse balance velocities accelerate rapidly within 100 km of the coast farther upstream balance velocities are consistent with both measured velocities along the egig traverse and calculated deformation velocities it is estimated that jakobshavns glacier discharges between 4 8 and 7 6 of the annual net balance over greenland and drains between 3 7 and 5 8 of the ice sheet area

modeling cyclic recession of cohesive clay coasts effects of wave erosion and bluff stability abstract a mathematical model combining the effects of wave erosion beach sediment and bluff slope stability has been developed to study the episodic cyclical recession of cohesive clay coasts the model was applied to the southern great lakes in north america which although non tidal experience seasonal fluctuations in lake level of about 0 5 m and long term fluctuations of up to 2 m model runs were designed to explore the interaction between various components of the system including profile shape bluff recession rates lake level variations beach morphodynamics the geomechanical characteristics of the material and the type slump topple and size of the slope failures model runs were made for the equivalent of 100 years quasi equilibrium conditions developed in the runs which had similar erosion rates to the field with parallel slope retreat in the upper portion of the profiles and slope decline in the lower portion temporal variations in the rate of recession of the crest of the bluff closely matched changes in lake level the model confirmed previous work that suggested that rates of bluff recession are strongly controlled by the rate of erosion below the water surface but it also provided support for a more recent proposal that rates of bluff recession also influence rates of erosion in shallow water it was found that positive and negative changes in the size of the beach can either promote or hinder bluff and profile erosion depending on local circumstances the model demonstrated that bluff height debris mobility wave undercutting and groundwater levels are key factors in determining the stability of coastal bluffs the model represents a promising new tool to forecast and thereby mitigate the effects of climate change on marine and lacustrine coasts

laboratory measurement of nearshore velocities and erosion of cohesive sediment till shorelines abstract the evolution of shorelines composed of consolidated cohesive sediments is dominated by irreversible erosion in this note measurements under laboratory conditions of bottom velocities wave heights and breaking characteristics over an actively eroding consolidated cohesive sediment shore are reported erosion is enhanced under breaking conditions and plunging breakers are markedly more erosive than spilling breakers the turbulence at the outer edge of the breaking zone has the 5 3 power high frequency dependence indicative of the inertial subrange

modelling the response of soft cliffs to climate change a statistical process response model using accumulated excess energy abstract cliff retreat poses a threat to coastal communities worldwide in soft cliff environments coastal retreat may occur at rapid rates the environmental significance of soft cliff environments coupled with the societal impacts of cliff retreat means that it is important to understand the processes and timings of soft cliff erosion here a new statistical process response model of soft cliff erosion is proposed based on the premise that wave energy delivered to the cliff toe is the key parameter forcing erosion more specifically and in contrast to prior studies that have sought to link erosion rates to indices of peak wave energy we postulate that the accumulated excess wave energy aee the time integrated total wave energy above an erosion threshold is the key hydraulic control on soft cliff erosion the new model is calibrated to two uk sites with contrasting atlantic versus north sea wave energy regimes before downscaled hadcm3 global climate model outputs are used to assess how future next 100 year changes in sea level and wave height affect retreat rates at the two study sites we show that the aee model accounts for between 46 and 89 of the variance in observed coastal erosion representing an improvement over prior models that use measures only of peak wave energy the aee model suggests increases of between 0 5 m a 1 92 and 0 3 m a 1 33 in mean erosion rate by 2100 for sites in the atlantic and north sea respectively furthermore it is shown that at both sites extreme events exceeding the 95th percentile value are projected to become three to four times more likely under scenarios of future climate change highlighting a need to understand and predict the extreme response of coastal cliff systems to changes in climate

the role of beach morphology on coastal cliff erosion under extreme waves erosion of hard rock coastal cliffs is understood to be caused by a combination of both marine and sub aerial processes beach morphology tidal elevation and significant wave heights especially under extreme storm conditions can lead to variability in wave energy flux to the cliff toe wave and water level measurements in the nearshore under energetic conditions are difficult to obtain and in situ observations are rare here we use monthly cliff face volume changes detected using terrestrial laser scanning alongside beach morphological changes and modelled nearshore hydrodynamics to examine how exposed cliffs respond to changes in extreme wave conditions and beach morphology the measurements cover the north atlantic storms of 2013 2014 and consider two exposed stretches of coastline porthleven and godrevy uk with contrasting beach morphology fronting the cliffs a flat dissipative sandy beach at godrevy and a steep reflective gravel beach at porthleven beach slope and the elevation of the beach cliff junction were found to influence the frequency of cliff inundation and the power of wave cliff impacts numerical modelling xbeach g showed that under highly energetic wave conditions i e those that occurred in the north atlantic during winter 2013 2014 with hs 5 5 m dissipative site and 8 m reflective site the combination of greater wave height and steeper beach at the reflective site led to amplified wave run up subjecting these cliffs to waves over 4 times as powerful as those impacting the cliffs at the dissipative site 39 kwm 1 compared with 9 kwm 1 this study highlighted the sensitivity of cliff erosion to extreme wave conditions where the majority over 90 of the annual value of cliff face erosion ensued during the winter the significance of these short term erosion rates in the context of long term retreat illustrates the importance of incorporating short term beach and wave dynamics into geomorphological studies of coastal cliff change

how does underlying geology affect coastline change an initial modeling investigation 1 conceptual geologic framework models predict that areas of the coast underlain by a weak or very fine grained lithology retreat landward faster than adjacent more resistant or coarser grained segments these apparently commonsense predictions seem inconsistent with observations that sandy coastlines underlain by heterogeneous lithology remain fairly smooth we have developed a numerical model to explore the interaction between shoreface lithology effects and alongshore transport processes on scales greater than years and kilometers shoreline indentations or sections of the coast that are slightly landward of adjacent sections tend to form in the model where the shoreface weathers more rapidly or is composed of finer grained material however alongshore transport tends to fill in these indentations slowing the weathering rates there while increasing them in adjacent areas where mobile sediment is preferentially removed over the long term this leads to an alongshore uniform retreat rate subtle shoreline undulations reflecting the heterogeneous geologic framework exist in the model but their amplitude reaches a steady state rather than increasing with time compositional heterogeneities determine the morphology of the coast while weathering rate heterogeneities control the thickness of sediment on the shoreface thus indentations can form in sections composed of harder less erodible rocks if they are finer grained

step wise changes in glacier flow speed coincide with calving and glacial earthquakes at helheim glacier greenland this is the publisher s version also available electronically from http onlinelibrary wiley com

measurement of historical cliff top changes and estimation of future trends using gis data between bridlington and hornsea holderness coast uk abstract a key requirement for effective coastal zone management is good knowledge of historical rates of change and the ability to predict future shoreline evolution especially for rapidly eroding areas historical shoreline recession analysis was used for the prediction of future cliff shoreline positions along a section of 9 km between bridlington and hornsea on the northern area of the holderness coast uk the analysis was based on historical maps and aerial photographs dating from 1852 to 2011 using the digital shoreline analysis system dsas 4 3 extension of esri s arcinfo 10 the prediction of future shorelines was performed for the next 40 years using a variety of techniques ranging from extrapolation from historical data geometric approaches like the historical trend analysis to a process response numerical model that incorporates physically based equations and geotechnical stability analysis with climate change and sea level rise implying that historical rates of change may not be a reliable guide for the future enhanced visualization of the evolving coastline has the potential to improve awareness of these changing conditions following the ipcc 2013 report two sea level rise rates 2 mm yr and 6 mm yr have been used to estimate future shoreline conditions this study illustrated that good predictive models once their limitations are estimated or at least defined are available for use by managers planners engineers scientists and the public to make better decisions regarding coastal management development and erosion control strategies

global comparison of benthic nepheloid layers based on 52 years of nephelometer and transmissometer measurements abstract global maps of maximum bottom particle concentration benthic nepheloid layer thickness and integrated particle mass in benthic nepheloid layers bnl based on 2412 global profiles collected using the lamont thorndike nephelometer from 1964 to 1984 are compared with maps of those same properties compiled from 6392 global profiles measured by transmissometers from 1979 to 2016 outputs from both instruments were converted to particulate matter concentration pm the purposes of this paper are to compare global differences and similarities in the location and intensity of bnls measured with these two independent instruments over slightly overlapping decadal time periods to combine the data sets in order to expand the time scale of global in situ measurements of bnls and to gain insight about the factors creating sustaining bnls the similarity between general locations of high and low particle concentration bnls during the two time periods indicates that the driving forces of erosion and resuspension of bottom sediments are spatially persistent during recent decadal time spans though in areas of strong bnls intensity is highly episodic topography and well developed current systems play a role these maps will help to understand deep ocean sediment dynamics linkage with upper ocean dynamics the potential for scavenging of adsorption prone elements near the seafloor and provide a comprehensive comparison of these data sets on a global scale during both time periods bnls are weak or absent in most of the pacific indian and atlantic basins away from continental margins high surface eddy kinetic energy is associated with the kuroshio current east of japan both data sets show weak bnls south of the kuroshio but no transmissometer data have been collected beneath the kuroshio itself sparse nephelometer data show moderate bnls just north of the kuroshio extension but with much lower concentrations than beneath the gulf stream strong bnls are found in areas where eddy kinetic energy in overlying waters mean kinetic energy near bottom and energy dissipation within the bottom boundary layer are high areas of strongest bnls include the western north atlantic argentine basin south atlantic areas around south africa tied to the agulhas current region and somewhat random locations in the antarctic circumpolar current of the southern ocean

natural and anthropogenic trace metals in sediments of the ligurian sea northwestern mediterranean abstract the magnitude and the chronology of anthropogenic impregnation by hg and other trace metals of environmental concern v cr ni cu zn ag cd and pb including its stable isotopes in the sediments are determined at the dyfamed station a site in the ligurian sea northwestern mediterranean chosen for its supposed open sea characteristics the dyfamed site vd is located on the right levee of the var canyon turbidite system at the end of the middle valley in order to trace the influence of the gravity current coming from the canyon on trace metal distribution in the sediment we studied an additional sediment core va from a terrace of the var canyon and material collected in sediment traps at the both sites at 20 m above sea bottom the patterns of hg and other trace element distribution profiles are interpreted using stable pb isotope ratios as proxies for its sources taking into account the sedimentary context turbidites redox conditions and sedimentation rates major element distributions coupled with the stratigraphic examination of the sediment cores point out the high heterogeneity of the deposits at va and major turbiditic events at both sites at the dyfamed site we observed direct anthropogenic influence in the upper sediment layer according to the 210pbxs derived sedimentation rate at the dyfamed site 0 4 mm yr 1 the hg enriched layer of the top core corresponds to the sediment accumulation of the last 50 years which is the period of the highest increase in hg deposition on a global scale with the hypothesis of the absence of significant post depositional redistribution of hg the hg corg ratio changes between the surface and below are used to estimate the anthropogenic contribution to the hg flux accumulated in the sediment the hg enrichment from pre industrial to the present time is calculated to be around 60 consistent with estimations of global hg models however based on the chemical composition of the trapped material collected in sediment traps we calculated that epibenthic mobilization of hg would reach 73 conversely the cd corg ratio decreases in the upper 5 cm which may reflect the recent decrease of atmospheric cd inputs or losses due to diagenetic processes

synchronous retreat and acceleration of southeast greenland outlet glaciers 2000 06 ice dynamics and coupling to climate a large portion of the recent increase in the rate of mass loss from the greenland ice sheet is from increased outlet glacier discharge along its southeastern margin while previous investigations of the region s two largest glaciers suggest that acceleration is a dynamic response to thinning and retreat of the calving front it is unknown whether this mechanism can explain regional acceleration and what forcing is responsible for initiating rapid thinning and retreat we examine seasonal and interannual changes in ice front position surface elevation and flow speed for 32 glaciers along the southeastern coast between 2000 and 2006 while substantial seasonality in front position and speed is apparent nearly all the observed glaciers show net retreat thinning and acceleration with speed up corresponding to retreat the ratio of retreat to the along flow stress coupling length is proportional to the relative increase in speed consistent with typical ice flow and sliding laws this affirms that speed up results from loss of resistive stress at the front during retreat which leads to along flow stress transfer large retreats were often preceded by the formation of a flat or reverse sloped surface near the front indicating that subsequent retreats were influenced by the reversed bed slope many retreats began with an increase in thinning rates near the front in the summer of 2003 a year of record high coastal air and sea surface temperatures this anomaly was driven in part by recent warming suggesting that episodes of speed up and retreat may become more common in a warmer climate

open ocean convection observations theory and models we review what is known about the convective process in the open ocean in which the properties of large volumes of water are changed by intermittent deep reaching convection triggered by winter storms observational laboratory and modeling studies reveal a fascinating and complex interplay of convective and geostrophic scales the large scale circulation of the ocean and the prevailing meteorology two aspects make ocean convection interesting from a theoretical point of view first the timescales of the convective process in the ocean are sufficiently long that it may be modified by the earth s rotation second the convective process is localized in space so that vertical buoyancy transfer by upright convection can give way to slantwise transfer by baroclinic instability moreover the convective and geostrophic scales are not very disparate from one another detailed observations of the process in the labrador greenland and mediterranean seas are described which were made possible by new observing technology when interpreted in terms of underlying dynamics and theory and the context provided by laboratory and numerical experiments of rotating convection great progress in our description and understanding of the processes at work is being made

an extensive western mediterranean deep water renewal between 2004 and 2006 1 the deep waters of the western mediterranean are known to have an almost constant trend towards higher salinity and temperature values since the 1950s recent observations have shown an acceleration of this tendency which has been attributed by some authors to the effect of the propagation of the signal of the eastern mediterranean transient from east to west from 2004 to 2006 five basin scale oceanographic cruises evidenced a relevant change in the deep structure of the western mediterranean in less than two years almost the whole deep basin has been filled with highly saline and warm new deep water which substantially renewed the resident deep water the paper shows evidence of the rapid basin wide extension of the event giving insights into the origin and the propagation of the new deep water towards the basin interior and showing the evolution of the deep characteristics

long term cliff retreat and erosion hotspots along the central shores of the monterey bay national marine sanctuary abstract quantification of cliff retreat rates for the southern half of santa cruz county ca usa located within the monterey bay national marine sanctuary using the softcopy geographic information system gis methodology results in average cliff retreat rates of 7 15 cm yr between 1953 and 1994 the coastal dunes at the southern end of santa cruz county migrate seaward and landward through time and display net accretion between 1953 and 1994 which is partially due to development in addition three critically eroding segments of coastline with high average erosion rates ranging from 20 to 63 cm yr are identified as erosion hotspots these locations include opal cliffs depot hill and manresa although cliff retreat is episodic spatially variable at the scale of meters and the factors affecting cliff retreat vary along the santa cruz county coastline there is a compensation between factors affecting retreat such that over the long term the coastline maintains a relatively smooth configuration the softcopy gis methodology significantly reduces errors inherent in the calculation of retreat rates in high relief areas e g erosion rates generated in this study are generally correct to within 10 cm by removing errors due to relief displacement although the resulting root mean squared error for erosion rates is relatively small simple projections of past erosion rates are inadequate to provide predictions of future cliff position improved predictions can be made for individual coastal segments by using a mean erosion rate and the standard deviation as guides to future cliff behavior in combination with an understanding of processes acting along the coastal segments in question this methodology can be applied on any high relief coast where retreat rates can be measured

a predictive mesoscale model of the erosion and profile development of soft rock shores the development application and behaviour of a generic model of retreating soft rock e g clay shores is described this represents a broad system in coastal modelling terms comprising shore platform beach tidal range wave transformation cliff and talus the coast is divided into a series of representative cross shore profiles each of which is discretised into a column of elements erosion of a platform element at each timestep depends on its gradient material strength is dealt with as a calibration constant wave forces are averaged over durations of a tide or hour and sediment transport is represented in bulk terms attention has been focussed on interaction between system parts and the emergence of system properties in particular profile shape this is allowed to develop towards dynamic equilibrium and is the principal means of model validation the emergence of the profile shape is dominated by the distribution of wave scour by the tide and by interaction with a beach if present because the model is process based it may be used to model the effects of climate change and engineering intervention yet it is also computationally inexpensive so may be used to explore uncertainty through probabilistic application the breadth of the included system coupled with short run times enables predictions over timescales of decades which we refer to as the mesoscale the model is used to explore the dynamics of retreating soft rock shore profiles and to predict future behaviour of a study site

impact of open sea deep convection on sediment remobilization in the western mediterranean 1 the northwestern mediterranean is known to be a privileged area of deep water formation via dense shelf water cascading and offshore convection the impact of the former in the sedimentary dynamics of the deep basin has been highlighted in recent years while open sea convection has been solely studied from a hydrological perspective particle fluxes and hydrodynamics were monitored at the dyfamed site ligurian sea western mediterranean at 200 1000 m and near the seafloor 2350 m depth during winter 2005 2006 from february to april 2006 and in coincidence with an unusual episode of deep water formation a notable intensification of currents was observed in the entire water column and near bottom particle flux increased up to two orders of magnitude these observations suggest that offshore convection must be taken into account together with cascading as a major driving force for sedimentary dynamics in the deep western mediterranean

tidally driven ice speed variation at helheim glacier greenland observed with terrestrial radar interferometry we used a terrestrial radar interferometer tri at helheim glacier greenland in august 2013 to study the effects of tidal forcing on the terminal zone of this tidewater glacier during our study period the glacier velocity was up to 25 m d 1 our measurements show that the glacier moves out of phase with the semi diurnal tides and the densely packed melange in the fjord here detrended glacier displacement lags behind the forecasted tidal height by 8 hours the transition in phase lag between the glacier and the melange happens within a narrow 500 m zone in the fjord in front of the ice cliff the tri data also suggest that the impact of tidal forcing decreases rapidly up glacier of the terminus a flowline model suggests this pattern of velocity perturbation is consistent with weak ice flowing over a weakly nonlinear bed

a review of terrestrial radar interferometry for measuring surface change in the geosciences this paper presents a review of the current state of the art in the use of terrestrial radar interferometry for the detection of surface changes related to mass movement different hardware types and acquisition concepts are described which use either real or synthetic aperture for radar image formation we present approaches for data processing procedures paying special attention to the separation of high resolution displacement information from atmospheric phase variations recent case studies are used to illustrate applications in terrestrial radar interferometry for change detection applications range from detection and quantification of very slow moving millimeters to centimeters per year displacements in rock walls from repeat monitoring to rapid processes resulting in fast displacements 50 m yr acquired during single measurement campaigns with durations of only a few hours fast and episodic acting processes such as rockfall and snow avalanches can be assessed qualitatively in the spatial domain by mapping decorrelation caused by those processes a concluding guide to best practice outlines the necessary preconditions that have to be fulfilled for successful application of the technique as well as in areas characterized by rapid decorrelation empirical data from a ku band sensor show the range of temporal decorrelation of different surfaces after more than two years for rock surfaces and after a few seconds to minutes in vegetated areas during windy conditions the examples show that the displacement field can be measured for landslides in dense grassland ice surfaces on flowing glaciers and snowpack creep copyright 2014 john wiley sons ltd

modeling the erosion of cohesive clay coasts a model was developed to study the erosion of cohesive clay coasts in macro to non tidal environments the model shares some of the characteristics of previous models including the erosion of bare clay surfaces by wave generated bottom shear stresses and of mobile sediment covered surfaces by abrasion it differs from previous models however in several important ways the morphodynamics of beaches with clay foundations under different wave conditions are based on a previously developed model for beaches on rocky shore platforms sediment thickness along a beach profile is calculated at regular intervals and compared with the maximum thickness that could be moved at that location under prevailing wave conditions wave friction factors are determined where necessary according to the occurrence and morphology of ripples on the bottom in addition to abrasion and the effect of wave induced shear stresses on the clay bottom erosion by stresses generated by wave impact at the bluff foot and on the intertidal platform is calculated using an expression derived from hard rock coastal models tides are represented by their computed tidal duration values the amount of time each year that the water level falls within each 0 1 m vertical interval water depths are modified by wave setup and set down conditions several preliminary model runs were made the profiles were concave in the submarine zone and roughly linear in the intertidal zone equilibrium profiles developed which were maintained as they migrated landwards

effects of varied lithology on soft cliff recession rates geomorphic modelling is a key method to understand the soft cliff recession process to predict future rates of retreat and responses to climate change a range of process based models have been used however the influence of varied vertical lithology has yet to be quantified this paper describes modifications to the 2d scape soft cliff and platform erosion model carried out to explore such interactions between vertical changes in cliff resistive strength and prevailing coastal conditions as expected weaker more resistant layers lead to more less rapid retreat however this effect is strongly influenced by the position of such layers relative to mean sea level where the erosive potential is greatest moreover model simulations reveal that layers of variable resistance give an asymmetric response in terms of both rates of retreat and the timeframe for the effect to be realised for example a reduction of material strength of 1 5 in comparison to the remainder of the cliff about mean sea level results in a rapid 130 increase in the rate of retreat in comparison to the introduction of a five times more resistant layer of the same characteristics this variation in response can be attributed to the different magnitudes of feedback governing profile reshaping associated with the change in lithology for example the introduction of a weaker layer amplifies erosion through its greater erosive potential combined with steepening of the overlying section the results have important implications for the management of coastal cliffs exhibiting variable stratigraphy combined with the potential for future interactions with sea level rise

equilibrium erosion of soft rock shores with a shallow or absent beach under increased sea level rise a process based numerical model was used to explore the response of soft rock shores with low volume beaches to variable rates of sea level rise equilibrium recession rates were simulated for ranges of wave height and period tidal amplitude rock strength beach volume and rate of sea level rise equilibrium shore profiles were found to be steeper with higher rates of sea level rise beaches were represented as protective surfaces yet were found to cause no significant reduction in equilibrium recession rate when their volumes were below a critical threshold reduced equilibrium recession rates were found with beaches that extended sufficiently far below low tide level the model results imply that given several constraints a very simple relationship exists between increased rates of sea level rise and the response of eroding composite soft rock low volume beach shores

equilibrium responses of cliffed coasts to changes in the rate of sea level rise abstract basic formulae have long been used to predict the effects of sea level rise on coastal recession for instance the geometric bruun rule and its modifications has often been applied to sandy coasts both low lying and steep however the behavior of rocky coasts whether strongly or poorly lithified should be significantly different than that of sandy coasts given that rocky coast evolution depends upon the irreversible breakdown of rock whereas sandy and depositional systems are controlled by the transport and related transport gradients of mobile sediment here we investigate the basis of a modeled relationship which suggests with a number of caveats that the equilibrium soft rock cliff recession rate can be estimated by the square root of the relative change in sea level rise rate although this relationship was derived using the numerical model scape soft cliff and platform erosion which simulates a broad soft rock cliffed coastal system driven by stochastic environmental forces here we show that a simplified modeling approach also reproduces the relationship we then extend this approach to develop a general theoretical framework within which it is possible to consider the potential responses of the different types of cliffed coasts to changes in the rate of sea level rise although a wide variety of processes affect different coastal settings this framework demonstrates how the strength and the nature of feedbacks within cliffed system control their response to sea level rise this suggests that cliffed environments controlled by different processes can still respond in similar ways to changes in the rate of sea level rise most rocky coasts would be expected to respond as a damped or negative feedback system between the extremes of a no feedback system that is unresponsive to sea level rise rate and an instant response system characterized by a linear response similar to the bruun rule this framework suggests that a potential inverse feedback case could also exist in which increased rates of sea level rise reduce the rate of coastal recession in almost all cases it is apparent that cliffed coast response to sea level rise depends not only upon the total elevation change of sea level but on the rate of the sea level rise these theoretical investigations and the classifications presented provide a framework to understand the behavior of systems affected by a wide array of processes and provide expectations that can be tested using more complex models of cliffed coast evolution in a variety of environments whether sandy or rocky hard or soft

high frequency of sediment gravity flow events in the var submarine canyon mediterranean sea this study aimed to analyze the role river floods play in triggering gravity flows and to investigate the role of submarine canyon systems as a conduit for terrigenous material to the deep sea two years of measurements in the var canyon at depths ranging from 1200 m to 2350 m indicate that six floods of the var river triggered hyperpycnal flows an important mechanism for transporting particulate matter to the deep sea floor these sediment gravity flows were characterized by a sudden increase of current velocity that lasted 8 to 22 h and by downward particle fluxes that reached up to 600 g m 2 d 1

continued evolution of jakobshavn isbrae following its rapid speedup 1 several new data sets reveal that thinning and speedup of jakobshavn isbrae continue following its recent rapid increase in speed as its floating ice tongue disintegrated the present speedup rate of 5 a 1 over much of the fast moving region appears to be a diffusive response to the initial much larger speedup near the front there is strong seasonality in speed over much of the fast flowing main trunk that shows a good inverse correlation with the seasonally varying length of a short typically 6 km floating ice tongue this modulation of speed with ice front position supports the hypothesis that the major speedup was caused by loss of the larger floating ice tongue from 1998 to 2003 analysis of image time series suggests that the transient winter ice tongue is formed when sea ice bonds glacier ice in the fjord to produce a nearly rigid mass that almost entirely suppresses calving major calving only resumes in late winter when much of this ice clears from the fjord the collapse of the ice tongue in the late 1990s followed almost immediately after a sharp decline in winter sea ice concentration in disko bay this decline may have extended the length of the calving season for several consecutive years leading to the ice tongue s collapse

radar interferogram filtering for geophysical applications the use of sar interferometry is often impeded by decorrelation from thermal noise temporal change and baseline geometry power spectra of interferograms are typically the sum of a narrow band component combined with broad band noise we describe a new adaptive filtering algorithm that dramatically lowers phase noise improving both measurement accuracy and phase unwrapping while demonstrating graceful degradation in regions of pure noise the performance of the filter is demonstrated with sar data from the ers satellites over the jakobshavns glacier of greenland

open ocean convection process a driver of the winter nutrient supply and the spring phytoplankton distribution in the northwestern mediterranean sea this study was a part of the dewex project deep water formation experiment designed to better understand the impact of dense water formation on the marine biogeochemical cycles here nutrient and phytoplankton vertical and horizontal distributions were investigated during a deep open ocean convection event and during the following spring bloom in the northwestern mediterranean sea nwm in february 2013 the deep convection event established a surface nutrient gradient from the center of the deep convection patch to the surrounding mixed and stratified areas in the center of the convection area a slight but significant difference of nitrate phosphate and silicate concentrations was observed possibly due to the different volume of deep waters included in the mixing or to the sediment resuspension occurring where the mixing reached the bottom one of this process or a combination of both enriched the water column in silicate and phosphate and altered significantly the stoichiometry in the center of the deep convection area this alteration favored the local development of microphytoplankton in spring whereas nanophytoplankton dominated neighboring locations where the convection reached the deep layer but not the bottom this study shows that the convection process influences both winter nutrients distribution and spring phytoplankton distribution and community structure modifications of the convection spatial scale and intensity i e convective mixing depth is likely to have strong consequences on phytoplankton community structure and distribution in the nwm and thus on the marine food web

dynamics of particles along the western margin of the southern adriatic processes involved in transferring particulate matter to the deep basin abstract the southern adriatic is an area of dense shelf water dsw cascading and open ocean convection the impact of dsw cascading events in transferring organic matter to the deep benthic community and in producing a wide range of bedforms along the continental margin has been highlighted in recent years in order to improve our knowledge on the interannual variability of the dsw cascading with the ultimate goal to understand timing of dsw formation and transport as well as the cascading process its variability in intensity and duration and the ultimate impact of the dense water on the deep sea in march 2009 we deployed an instrumented mooring in a field of sediment waves 860 m depth located down current to the bari canyon in march 2010 a second mooring was installed in the northern channel of the canyon winters 2009 2010 and 2011 were mild and particularly wet and the po river discharge remained relatively high throughout the whole winter hence we expected weak dense shelf water formation associated with a shallow shelf water overflowing off the adriatic shelf by contrast in winter 2012 the north adriatic experienced a severe cold wave with ne bora winds and reduced fresh water input these weather conditions allowed the formation of extremely dense shelf water three additional moorings were quickly deployed during this cold event in the southern adriatic sea to investigate the spatial variability of particle and organic matter fluxes exiting from the adriatic continental shelf under the influence of a strong dsw cascading event slow near bottom currents never exceeding 40 cm s 1 were recorded between march 2009 and february 2012 water temperatures depicted minor negative shifts total mass fluxes tmfs were low annual avg 1 7 2 8 g m 2 d 1 and 0 3 0 6 g m 2 d 1 in the canyon and in the sediment wave field respectively and peak values 6 8 g m 2 d 1 but showed significant seasonal and interannual variability fluxes in the canyon were higher than those measured in the sediment wave field at deeper water depth mass flux peaks during the 2112 dsw cascading were up to 5 times higher than the peaks of previous years up to 18 70 g m 2 d 1 with a spatial variability mainly driven by the localized pathways of dsw cascading in the canyon near bottom currents exceeded 70 cm s 1 and temperature dropped to 12 2 c while current speeds were high also at 1200 m depth 60 cm s 1 in the moat surrounding the dauno seamount surprisingly mass flux peaks occurred from the 16th february to the 1st of march 3 4 weeks ahead of the usual dsw occurrence suggesting an early arrival of the dsw the deep dsw cascading was the main process driving the particle transfer across the southern adriatic margin during late winter spring 2012 mooring data showed a nw se gradient of temperature and kinetic energy from upslope to basin floor indicating slope transverse flow modulated by local obstruction caused by the rugged seafloor topography bari canyon is one of the sites of dsw flow and in this area we have the possibility to extend observations back in time using continuous mooring data since 2009 and previous published materials this approach allowed evaluation of additional mechanisms of particle transport e g open ocean convection storm driven downward transport shallow dense water cascading that are particularly relevant in years when the dsw formation is less vigorous and cascading processes are sluggish the small amplitude of total mass flux peaks the weak currents and the relatively high and constant temperatures recorded during 2009 2010 and 2011 springs are consistent with an enhanced vertical particle rain from a mid water nepheloid layer triggered in turn by a shallow cascading of not particularly dense shelf water detaching from the seafloor when reaches its neutral buoyancy thus the intensity of dsw cascading shallow vs deep plays a first order control on the particulate fluxes through the western margin of the southern adriatic while storm induced sediment transport can occasionally be relevant too

sediment transport to the deep canyons and open slope of the western gulf of lions during the 2006 intense cascading and open sea convection period an array of mooring lines deployed between 300 and 1900 m depth along the lacaze duthiers and cap de creus canyons and in the adjacent southern open slope was used to study the water and sediment transport on the western gulf of lions margin during the 2006 intense cascading period deep reaching cascading pulses occurred in early january in late january and from early march to mid april dense water and sediment transport to the deep environments occurred not only through submarine canyons but also along the southern open slope during the deep cascading pulses temporary upper and mid canyon and open slope deposits were an important source of sediment to the deep margin significant sediment transport events at the canyon head only occurred in early january because of higher sediment availability on the shelf after the stratified and calm season and in late february because of the interaction of dense shelf water cascading with a strong e se storm during the january deep cascading pulses increases in suspended sediment concentration within the canyon were greater and earlier at 1000 m depth than at 300 m depth whereas during the march april deep cascading pulses sediment concentration only increased below 300 m depth indicating resuspension and redistribution of sediments previously deposited at upper and mid canyon depths deeper than 1000 m depth net fluxes show that most of the suspended sediment left the canyon and flowed along the southern open slope towards the catalan margin whereas a small part flowed down canyon and was exported basinward additionally on the mid and lower continental slope there was an increase in the near bottom currents induced by deep open sea convection processes and the propagation of eddies this combined with the arrival of deep cascading pulses also generated moderate suspended sediment transport events in the deeper slope regions

modeling cohesive clay coast evolution and response to climate change a model was used to study the evolution of cohesive clay coasts under different environmental and geological conditions and the effect of future climate change the model considered wave impact on the bluff and in the intertidal zone and bottom generated shear stresses and the protective and abrasive action of beach sediment in the intertidal and subtidal zones quasi equilibrium conditions developed in model runs with parallel slope retreat in the upper portion of the profiles and slope decline in the lower portions profile gradient below the low tidal level increased with the threshold shear stress for bottom erosion therefore rates of wave attenuation were lower in resistant than in weak materials and the intertidal zones were wider and more gently sloping the widest and gentlest intertidal zones developed in runs that had no sediment the largest waves played little role in platform development in part because of low frequency but mainly because they expend most of their energy in crossing wide turbulent surf zones the model suggested that rising sea level will usually result in accelerated rates of bluff recession especially if the rise is rapid simultaneous increases in the frequency of moderately large waves as opposed to the largest waves may also generate marked increases in erosion on bluffs and in intertidal and supratidal zones although erosion may be reduced at some elevations where there is beach sediment positive or negative changes in beach volume can increase or decrease rates of bluff erosion