Search

Abstract: This paper investigates the effect of future sea-level rise (SLR) on the tides of the northwest European Continental Shelf. The European shelf tide is dominated by semidiurnal constituents. This study therefore focuses primarily on the changes in the M2 tidal constituent and the spring and neap tidal conditions. The validated operational Dutch Continental Shelf Model is run for the present day sea-level as well as 2 and 10m SLR scenarios. The M2 tidal amplitude responds to SLR in a spatially non-uniform manner, with substantial amplitude increases and decreases in both scenarios. The M2 tidal response is non-linear between 2 and 10m with respect to SLR, particularly in the North Sea. Under the 2m SLR scenario the M2 constituent is particularly responsive in the resonant areas of the Bristol Channel and Gulf of St. Malo (with large amplitude decreases) and in the southeastern German Bight and Dutch Wadden Sea (with large amplitude increases). Changes in the spring tide are generally greater still than those in the M2 or neap tides. With 2m SLR the spring tidal range increases up to 35cm at Cuxhaven and decreases up to −49cm at St. Malo. Additionally the changes in the shallow water tides are larger than expected. With SLR the depth, wave speed and wave length (tidal resonance characteristics) are increased causing changes in near resonant areas. In expansive shallow areas SLR causes reduced energy dissipation by bottom friction. Combined these mechanisms result in the migration of the amphidromes and complex patterns of non-linear change in the tide with SLR. Despite the significant uncertainty associated with the rate of SLR over the next century, substantial alterations to tidal characteristics can be expected under a high end SLR scenario. Contrary to existing studies this paper highlights the importance of considering the modification of the tides by future SLR. These substantial future changes in the tides could have wide reaching implications; including for example, correctly calculating design level requirements for flood defences, the availability of tidal renewable energy and dredging requirements. [Copyright &y& Elsevier]

Abstract: This paper provides estimates of rates of change in mean sea level around the English Channel, based on an extensive new hourly sea level data set for the south coast of the UK, derived from data archaeology. Mean sea level trends are found to vary by between 0.8 and 2.3mm/yr around the Channel. The rates of mean sea level change are calculated by removing the coherent part of the sea level variability from the time series of annual mean sea level before fitting linear trends. The improvement in accuracy gained by using this approach is assessed by comparing trends with those calculated using the more traditional method, in which linear trends are fitted directly to the original records. Removal of the coherent part of the sea level variability allows more precise trends to be calculated from records spanning 30 years. With the traditional approach 50 years is required to obtain the same level of accuracy. Rates of vertical land movement are approximated by subtracting the mean sea level trends from the most recent regional estimate of change in sea level due to oceanographic processes only. These estimated rates are compared to measurements from geological data and advanced geodetic techniques. There is good agreement around most of the UK. However, the rates estimated from the sea level records imply that the geological data suggest too much submergence along the western and central parts of the UK south coast. Lastly, the paper evaluates whether the high rates of mean sea level rise of the last decade are unusual compared to trends observed at other periods in the historical record and finds that they are not. [Copyright &y& Elsevier]

CoastSnap is a low-cost community beach monitoring program that turns everyday smartphones into devices to measure coastal response to storms, sea-level rise, human modifications and other factors. Underpinning CoastSnap is a stainless-steel smartphone cradle that is installed overlooking a beach in a location easily accessible to the public. Using the cradle for image positioning, passers-by simply take a photo of the coast and upload it to a centralized database, which in turn provides a crowd-sourced record of coastline change over time. Behind this simple idea are advanced image processing algorithms that then enable the shoreline position (and other coastal features) to be mapped from the community snapshots in a scientifically rigorous manner. First established in Sydney, Australia in 2017, the network of CoastSnap stations has grown rapidly over the past five years to now encompass 200 monitoring locations in 21 countries. Analysis of the 44 Australian stations managed by the Authors indicates strong community participation, with over 10,000 images and 4000 community participants to date and an image submission frequency ranging from approximately weekly to daily (average = 2.6 images/station/week). Example practical applications of CoastSnap include: as a tool to monitor high-frequency shoreline change and coastal inlet dynamics; to support conservation efforts on protected coastlines; and to directly inform the timing of dredging and beach nourishment activities. This paper describes the background and evolution of the project and discusses its successes, challenges as well as future directions. • CoastSnap demonstrates how community smartphone images can accurately monitor coastal change. • Global CoastSnap network now comprises 200 stations in 21 countries. • Participation statistics in Australia indicate strong community uptake (weekly to sub-daily imagery). [ABSTRACT FROM AUTHOR]

Abstract: The impacts of rising mean sea levels will be felt most acutely during periods of extreme high sea levels which are caused by the combination of mean sea level, tides and storm surges. In this paper, we examine sea level records from six tide gauges along the German North Sea coastline to determine if changes in high sea levels observed throughout the 20th century and early 21st century were primarily driven by increases in mean sea level (i.e. like what has been observed by other authors in most parts of the world) or whether other factors, such as changes in ocean tides or storm surges also contributed significantly to observed changes in high water in this region. Time-series of annual 80th, 85th, 90th, 95th, 99th, and 99.9th percentiles are derived from the sea level records and trends are assessed using linear regression for the entire time periods for which datasets are available at each site and for the common period from 1953 to 2008. The percentile time-series are subsequently reduced relative to mean sea level and a second set of trends are estimated. At all sites and percentile levels, significant positive trends are evident for the observed sea level data. Once the percentile time-series are reduced relative to mean sea level the remaining trends are still significant at the 1σ-confidence level, with the exception of the 99.9th percentiles since the standard errors are large. Using a non-linear trend analysis, on the long Cuxhaven record, we find that prior to the mid-1950s and from about 1990 onwards, changes in high sea levels were not different from mean sea level changes. However, from the mid-1950s to 1990 changes were significantly different from those observed in mean sea level. Possible reasons for this appear to be due to changes in the amplitudes of several main tidal constituents, which are apparent since the mid-1950s and decadal variability in the storm activity (with strong westerly winds in the North Atlantic region from 1960 to the 1990s). [Copyright &y& Elsevier]

Abstract: The possibility of Holocene subsidence along the northern coast of the Corinth Gulf is often mentioned in the literature; however, systematic detailed evidence that submergence (e.g. of archaeological remains) does not simply depend from eustatic sea-level rise is most often missing. In this paper, a new detailed study of submerged tidal-notch profiles along the limestone coast has shown that periods of sea-level stability are intercalated with periods of rapid subsidence or gradual relative sea-level rise. It appears that most of the sites considered, seem to have been affected by a relatively recent co-seismic subsidence of about half a meter, whereas during the longer period, by stages of relative sea-level stability and/or gradual relative sea-level rise. This evidence of subsidence is confirmed by radiocarbon dating in doline sediments, suggesting that during certain periods, a relative sea-level rise was much faster than the raising suggested by glacio-eustatic or hydro-isostatic estimations. Juxtaposing a list of known earthquakes occurred in the area shows that several earthquakes (e.g. the 1981 one for the easternmost sites considered) are potential candidates for the recent co-seismic displacements and thus supporting the geomorphological interpretations. [Copyright &y& Elsevier]

Abstract: The paper documents characteristics of the fundamental Adriatic seiche (period of 21.5h) by analysing hourly sea level data at Split and Rovinj in 1957–2002 interval. The seiche is extracted by digital filter from residual (detided) sea level series. Basic statistics, both on seasonal and interannual scale, as well as flood (threshold-exceeding) analysis has been performed in order to visualise the importance of the seiche. Although mean seiche variance is as small as 2–3%, seiche energy can be much larger than tidal energy during extreme events. The largest seiche amplitudes occur in February and March, being almost two times smaller in summer season. A decrease of seiche flood amplitudes in time has been documented, coinciding with a decrease in the storm surge height. This is presumably due to weakening of atmospheric activity during investigated period. However, a reversal in that trend may result in disastrous and exceptionally high floods in the future, due to coupling with the global sea level rise and its regional (Adriatic) manifestation. [Copyright &y& Elsevier]

Abstract: This paper describes the development of a model for prediction of local changes in morphodynamics resulting from managed realignment, undertaken as part of a UK project funded by Defra. The methodology builds on the conceptual modelling approach to habitat development employed successfully by , and others for lagoon environments. The overall approach can be described as hybrid – combining bottom-up (process-based) and top-down (simplified and/or empirical) predictive techniques – to describe the essential inlet functioning. The model described in this paper is used to predict the evolution of a managed realignment site under the action of tides and waves and sediment supply. Validation of the managed realignment model is undertaken using the available survey data from before the realignment and from several years afterwards. The performance of the model is promising in this respect, producing the right magnitude and the main qualitative features of bathymetric change. Longer simulations are used to see how the growth of saltmarsh itself affects the evolution of the setback field and how sea level rise would affect the development of saltmarsh. [Copyright &y& Elsevier]