Increase In Mean Sea Level Research Articles

Modelling of Storm Impacts on the Shandong Peninsula Coast

ABSTRACT Dalledonne, G. L., and Mayerle, R., 2016. Modelling of storm impacts on the Shandong peninsula coast. This paper presents results of the investigation of the effect of storms on the morphodynamics of the Yantai coastal areas in the Shandong Peninsula, China. A two-dimensional depth integrated morphodynamic model for prediction of the morphological changes during extreme events was developed and applied. The model covers the entire Bohai Sea with increasing grid resolution towards the coastal areas near Yantai. Calibration and validation using tidal constituents and measured water levels and current velocities showed that the model is capable of predicting the hydrodynamics in good agreement with observations. Emphasis was given to the proper description of the spatial distribution of the seabed sediments and bed stratigraphy. The 20 most severe storms observed in the region from 2000 to 2013 were identified and reconstructed. Storm surges with increases in mean sea level of up to 1.7 m and signif...

Nálisis multitemporal de la línea de costa en la isla de Tierrabomba y proyección del mapa de inundación por aumento del nivel medio del mar

A space-time study of the coastline of the island of Tierrabomba was performed by analyzing satellite images, aerial photographs and orthophotos for the period 1954-2013 provided by the Center for Oceanographic and Hydrographic Research Caribbean - CIOH. This tool was used as a System of Geographic Information Systems (GIS) for Georeferencing images and digitized shorelines, making a division of the island into five sectors to identify areas of erosion and accretion rate with their respective Annual change by End Point Method (EPR) and identification of flood zones by the projection of the increase in mean sea level with an increasing trend of 5.3mm+0.3mm yr-1 using a digital elevation model into the tool GIS data with LIDAR (Ligth Detection and Ranging). It was observed that the general trend of the shoreline is eroding with accretion areas generated by anthropogenic craft works developed by the natives, the maximum erosion rate was 2.22mts yr-1 in the sector "Charlie" (northern Island) and the maximum accretion was 1.31mts yr-1 in the sector "Delta" (east side of the island) industry for a total of 52.5 and 10.1 Ha eroded accretion during 1954-2013. The areas identified as flood zones by increasing the mean sea level coincided with marshes and coastal lagoons that the natives of the region called "Salinas". each proposed scenario. The dynamic regionalization of the island of Santo Domingo allowed to identify surface mesoscale oceanographic structures as eddies and filaments for the month of February 2005.

Rapid rise in effective sea-level in southwest Bangladesh: Its causes and contemporary rates

Evidence is presented from three estuarine tide gauges located in the Sundarban area of southwest Bangladesh of relative sea level rise substantially in excess of the generally accepted rates from altimetry, as well as previous tide-gauge analyses. It is proposed that the difference arises from the use of Relative Mean Sea Level (RMSL) to characterise the present and future coastal flood hazard, since RMSL can be misleading in estuaries in which tidal range is changing. Three tide gauges, one located in the uninhabited mangrove forested area (Sundarban) of southwest Bangladesh, the others in the densely populated polder zone north of the present Sundarban, show rates of increase in RMSL ranging from 2.8mma−1 to 8.8mma−1. However, these trends in RMSL disguise the fact that high water levels in the polder zone have been increasing at an average rate of 15.9mma−1 and a maximum of 17.2mma−1. In an area experiencing tidal range amplification, RMSL will always underestimate the rise in high water levels; consequently, as an alternative to RMSL, the use of trends in high water maxima or ‘Effective Sea Level Rise’ (ESLR) is adopted as a more strategic parameter to characterise the flooding hazard potential. The rate of increase in ESLR is shown to be due to a combination of deltaic subsidence, including sediment compaction, and eustatic sea level rise, but principally as a result of increased tidal range in estuary channels recently constricted by embankments. These increases in ESLR have been partially offset by decreases in fresh water discharge in those estuaries connected to the Ganges. The recognition of increases of the effective sea level in the Bangladesh Sundarban, which are substantially greater than increases in mean sea level, is of the utmost importance to flood management in this low-lying and densely populated area.

Characteristics of large positive and negative surges in the Mediterranean Sea and their attenuation in future climate scenarios

This study analyzes large positive and negative storm surges along the Mediterranean coast in a 7-member climate model ensemble covering the period 1951–2050 under the A1B emission scenario. A hydro-dynamical shallow water model (HYPSE, Hydrostatic Padua Sea Elevation model) is driven by 6-hourly meteorological fields produced by the state-of-the-art global and regional climate models that have been used in the CIRCE fp6 project (Climate Change and Impact Research: the Mediterranean Environment). Model validation is based on the comparison of a model hindcast (1958–2001) and climate simulations with observed sea level (SL) values at 21 tide gauges. The accuracy of the models in reproducing large positive and negative storm surges appears to depend primarily on the quality of the atmospheric forcing (which is mainly related to their space resolution). Also the resolution of the hydro-dynamical model is somehow relevant along some stretches of the coastline. Climate signal is computed as the difference between the surge statistics in the 2021–2050 and 1971–2000 periods. The choice of the global climate simulation, which is used for the boundary conditions of the regional climate models, is shown to be the largest source of uncertainty for the assessment of the climate change signal. Other, less relevant, sources of uncertainty are the choice of the regional climate model and that of the hydro-dynamical model resolution. In spite of these uncertainties, the model ensemble mean shows a modest (about −5%), but clear and widespread decrease of the amplitude of both positive and negative large storm surges along the coast of the Mediterranean Sea. However, increase of mean SL and land subsidence (which are not considered in this study) might increase significantly the hazard posed by coastal floods in spite of the likely attenuation of storminess that is caused by climate change in the Mediterranean Sea.

Trends in high sea levels of German North Sea gauges compared to regional mean sea level changes

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).

Climate Change Impacts on the Stability of Small Tidal Inlets: A Numerical Modelling Study Using the Realistic Analogue Approach

Tidal inlets are of great societal importance as they are often associated with ports and harbours, industry, tourism, recreation and prime waterfront real estate. Their behaviour is governed by the delicate balance of oceanic processes (tides, waves and mean sea level), and fluvial/estuarine processes (riverflow and heat fluxes), all of which can be significantly affected by climate change (CC) processes. This study investigates the potential range of CC impacts on the stability (closed/open state and locational stability) via the application of a sophisticated process based morphodynamic model (Delft3D) to strategically selected schematized inlet morphologies and forcing conditions. Results show that, under worst case scenario conditions, the integrated effect of climate change driven increase in mean sea level, wave height and wave angle may significantly change inlet stability condition.

Changing North Sea storm surge climate: An increasing hazard?

Extreme sea levels provide a substantial hazard for low lying coastal areas in the Southern North Sea. They are caused by a combination of different factors such as high astronomical tides, a large-scale rise of the sea surface caused by high wind speeds and low atmospheric pressure (usually referred to as storm surges), or extreme wind-generated waves (sea states) caused by high wind speeds in atmospheric low pressure systems; that is extra-tropical storms. Long-term changes in any of these factors may substantially alter the hazard associated with extreme sea levels. Moreover, any long-term change in mean sea level such as observed over the past 100 years or as associated with future anthropogenic climate change will have an impact as it shifts the entire distribution of sea levels towards higher values; that is, it changes the baseline upon which storm induced sea levels have to be added. Moreover, in shallow waters non-linear interaction effects may occur. Here we review the present knowledge about long-term changes in any of these factors. We show that storm activity in the area underwent considerable variations on time scales of decades and longer, but that no clear long-term trend could be identified. Similar findings are obtained for long-term changes in the storm surge and wave climate. Mean sea level has increased in the Southern North Sea over the past centuries. Correspondingly an increase in extreme sea levels is found. For the future most projections point towards a moderate increase in storm activity in the area with corresponding changes in storm surge and wave climate. These changes will add to the expected future increase in mean sea level, leading to an increased hazard from extreme sea levels. The latter may have consequences for safety, especially in the low lying coastal areas in the Southern North Sea. Consequences for coastal protection and alternative strategies are discussed.

Storm surges in the Western Baltic Sea: the present and a possible future

Globally-coupled climate models are generally capable of reproducing the observed trends in the globally averaged atmospheric temperature or mean sea level. However, the global models do not perform as well on regional/local scales. Here, we present results from four 100-year ocean model experiments for the Western Baltic Sea. In order to simulate storm surges in this region, we have used the General Estuarine Transport Model (GETM) as a high-resolution local model (spatial resolution ≈ 1 km), nested into a regional atmospheric and regional oceanic model in a fully baroclinic downscaling approach. The downscaling is based on the global model ECHAM5/MPI-OM. The projections are imbedded into two greenhouse-gas emission scenarios, A1B and B1, for the period 2000–2100, each with two realisations. Two control runs from 1960 to 2000 are used for validation. We use this modelling system to statistically reproduce the present distribution of surge extremes. The usage of the high-resolution local model leads to an improvement in surge heights of at least 10% compared to the driving model. To quantify uncertainties associated with climate projections, we investigate the impact of enhanced wind velocities and changes in mean sea levels. The analysis revealed a linear dependence of surge height and mean sea level, although the slope parameter is spatially varying. Furthermore, the modelling system is used to project possible changes within the next century. The results show that the sea level rise has greater potential to increase surge levels than does increased wind speed. The simulations further indicate that the changes in storm surge height in the scenarios can be consistently explained by the increase in mean sea level and variation in wind speed.

Increased sea level promotes coral cover on shallow reef flats in the Andaman Sea, eastern Indian Ocean

Sea level in the Indian Ocean is subject to considerable temporal and spatial variabilities. During the period 1960–2009 at Phuket, Thailand, in the NE Indian Ocean, mean sea level increased by 2.7 mm y−1. Regular monitoring of coral cover on fringing reef flats at Phuket since 1979 revealed a sensitive response of this habitat to both transient sea-level depressions and sea-level elevation. Since 1987 when more frequent sampling began, coral cover was positively correlated with the mean sea level experienced over the preceding months. Changing mean sea level explained a high proportion of the observed variation in cover, with overall increasing sea levels and a lack of negative sea-level anomalies promoting cover on the outer reef flats. Concomitantly, there have been no changes in reef community structure or any apparent shifts in zonation patterns across the reef. While future benefits of continued increases in mean sea level on reef flats in the region will be constrained by the frequency and intensity of sea-level depressions associated with the Indian Ocean Dipole, and bleaching events, the overall picture for these shallow reefs is a positive one as they respond to increasing sea level and show rapid recovery from environmental disturbances.

Past and future plant diversity of a coastal wetland driven by soil subsidence and climate change

On the island of Ameland (The Netherlands), natural gas has been ex- tracted from a dune and salt marsh natural area since 1986. This has caused a soil subsidence of c. 1-25 cm, which can be used as a model to infer effects of future sea level rise. The aims of our study were (a) to relate the changes in the vegetation, and more specifically, in plant diversity, during the extraction period to soil subsidence and weather fluctuations, and (b) to use these relations to predict future changes due to the combination of ongoing soil subsidence and climate change. We characterised climate change as increases in mean sea level, storm frequency and net precipitation. Simultaneous observations were made of vegetation composition, elevation, soil chemistry, net precipitation, groundwater level, and flooding frequency over the period 1986-2001. By using multiple regression the changes in the vegetation could be decomposed into (1) an oscillatory component due to fluctuations in net precip- itation, (2) an oscillatory component due to incidental flooding, (3) a monotonous component due to soil subsidence, and (4) a monotonous component not related to any measured variable but probably due to eutrophication. The changes were generally small during the observation period, but the regression model predicts large changes by the year 2100 that are almost exclusively due to sea level rise. However, although sea level rise is expected to cause a loss of species, this does not necessarily lead to a loss of conservancy value.

Long Term Decline of a Common Tern (Sterna hirundo) Population Nesting in Salt Marshes in Venice Lagoon, Italy

Each year between 1989 and 2008, I monitored Common Tern colonies in the lagoon of Venice (Italy). This population nests only on salt marsh islets, which are subjected to flooding during high tides. The number of breeding pairs decreased significantly from 832 to 109, with an average rate of decrease of −10.1%. Overall, 188 colonies were found, ranging from two to 583 pairs; median colony size was 57 pairs, and it decreased significantly. The mean turnover rate was high at 41.5%, and it ranged each year between 7.7% and 60%. The observed trends could be attributed to the increase in mean sea level that occurred over the last 20 years (0.5 cm/yr). In the May–June period, the number of days with high tides leading to a complete flooding of the breeding site increased. Between 1989 and 1998 there was on average 4.4 days with floodings. This increased to 8.4 days between 1999 and 2008. Therefore, sea level rise could be a major contributor to declining Common Tern populations in the lagoon of Venice.

Holocene sea-level changes along the North Carolina Coastline and their implications for glacial isostatic adjustment models

We have synthesized new and existing relative sea-level (RSL) data to produce a quality-controlled, spatially comprehensive database from the North Carolina coastline. The RSL database consists of 54 sea-level index points that are quantitatively related to an appropriate tide level and assigned an error estimate, and a further 33 limiting dates that confine the maximum and minimum elevations of RSL. The temporal distribution of the index points is very uneven with only five index points older than 4000 cal a BP, but the form of the Holocene sea-level trend is constrained by both terrestrial and marine limiting dates. The data illustrate RSL rapidly rising during the early and mid Holocene from an observed elevation of −35.7 ± 1.1 m MSL at 11062–10576 cal a BP to −4.2 m ± 0.4 m MSL at 4240–3592 cal a BP. We restricted comparisons between observations and predictions from the ICE-5G(VM2) with rotational feedback Glacial Isostatic Adjustment (GIA) model to the Late Holocene RSL (last 4000 cal a BP) because of the wealth of sea-level data during this time interval. The ICE-5G(VM2) model predicts significant spatial variations in RSL across North Carolina, thus we subdivided the observations into two regions. The model forecasts an increase in the rate of sea-level rise in Region 1 (Albemarle, Currituck, Roanoke, Croatan, and northern Pamlico sounds) compared to Region 2 (southern Pamlico, Core and Bogue sounds, and farther south to Wilmington). The observations show Late Holocene sea-level rising at 1.14 ± 0.03 mm year −1 and 0.82 ± 0.02 mm year −1 in Regions 1 and 2, respectively. The ICE-5G(VM2) predictions capture the general temporal trend of the observations, although there is an apparent misfit for index points older than 2000 cal a BP. It is presently unknown whether these misfits are caused by possible tectonic uplift associated with the mid-Carolina Platform High or a flaw in the GIA model. A comparison of local tide gauge data with the Late Holocene RSL trends from Regions 1 and 2 support the spatial variation in RSL across North Carolina, and imply an additional increase of mean sea level of greater than 2 mm year −1 during the latter half of the 20th century; this is in general agreement with historical tide gauge and satellite altimetry data.

Sea Levels at Newlyn 1915–2005: Analysis of Trends for Future Flooding Risks

It is sometimes assumed that changes in risks of coastal flooding can be computed by just adding mean sea level changes to existing statistics of tidal and meteorological effects. This assumption can be examined by looking at trends in separate tidal and nontidal sea levels, but suitable sites with long records of good quality sea level measurements are rare. As an example, hourly sea level data from the well-maintained tide gauge at Newlyn in southwest England has been critically edited for errors and separated into tidal, nontidal, and mean sea level components. These components have then been analysed for significant trends, and possible correlations with meteorological indicators. There is a small (0.16 mm y−1) increase in standard deviation of the observations, and consistent increases in the M2 and M4 tidal amplitudes. An apparent reduction in the standard deviation of the nontidal residuals can be attributed to a change to a different measuring system in 1984, as can a sudden decrease of 2° (4 min earlier) in the phase lag of M2. There are weak correlations between nontidal (surge) statistics and meteorological parameters, including the North Atlantic oscillation (NAO). Observed annual maximum sea levels are increasing at a rate not significantly different from the observed increase in mean sea level of 1.77 ± 0.12 mm y−1. These very exact analyses of a high-quality consistent long sea level series may indicate limits on the types of trends to be expected elsewhere in the region. Application of this type of analysis for estimating future flooding risks is discussed.

Sea level characteristics in the Bay of Fundy/Gulf of Maine

AbstractThis article reports on the analysis of sea level records from the Bay of Fundy/Gulf of Maine. Descriptive statistical methods are used to illustrate the increase in mean sea level, seasonal variance and nodal variation. Frequency domain time series methods are used to model increasing tidal amplitude, and to characterize features of sea level spectra. Copyright © 2004 John Wiley & Sons, Ltd.

Present-Day Sea Level Change: Observations and Causes

We investigate climate-related processes causing variations of the global mean sea level on interannual to decadal time scale. We focus on thermal expansion of the oceans and continental water mass balance. We show that during the 1990s where global mean sea level change has been measured by Topex/Poseidon satellite altimetry, thermal expansion is the dominant contribution to the observed 2.5 mm/yr sea level rise. For the past decades, exchange of water between continental reservoirs and oceans had a small, but not totally negligible contribution (about 0.2 mm/yr) to sea level rise. For the last four decades, thermal contribution is estimated to about 0.5 mm/yr, with a possible accelerated rate of thermosteric rise during the 1990s. Topex/Poseidon shows an increase in mean sea level of 2.5 mm/yr over the last decade, a value about two times larger than reported by historical tide gauges. This would suggest that there has been significant acceleration of sea level rise in the recent past, possibly related to ocean warming.

Historical changes of bottom topography and tidal amplitude in the Ria de Aveiro, Portugal–trends for future evolution

The natural evolution of the estuary-coastal lagoon system of the Ria de Aveiro, Portu- gal, was halted in 1808 by the construction of a new inlet/outlet channel through the sand spit which isolates it from the Atlantic Ocean. In consequence, tidal amplitudes in the lagoon increased from 0.07-0.13 m to over 1 m. Improvements to the channel since 1936, including construction of jetties, breakwaters and dredging, have increased its cross-sectional area. This has caused a steady increase in tidal amplitude to between 2.5 and 2.8 m, the erosion of mud flats, salt marsh and old salt pans, the widening and deepening of channels, and a greater capacity for sediment transport and dispersal due to the increased tidal currents. The volume of the tidal prism calculated for spring tides is now 1.7 times that in 1951; thus areas bordering the lagoon, especially agricultural fields, are experiencing a progressively increasing risk of flooding and salt water contamination at high water. Any future increase of mean sea level will contribute to an increase of both area and volume of the water mass and could cause important changes to the dynamics of the system. An increase in mean sea level of 0.1 m will, for example, correspond to an increase of 5% in the capacity of the system and contribute to an increase in the speed of tidal propagation. The resulting increase in the volume of the tidal prism will be up to 22% of the present maximum value.

Scale analysis to sort the different causes of mean sea level changes: An application to the northern Adriatic Sea

The variations in the relative sea level occur at very different scales both in space and time and reflect the combined variations of the absolute sea and land levels. An effective separation between these and the identification of the single physical processes responsible for the sea level changes observed in a given region and period of time can be achieved through a scale analysis. While the spatial extent of the phenomenon is characterized by comparing statistically the data at local, regional and global scales, the time extent is characterized by studying the different regimes in the series through a nonparametric change‐point algorithm. The details of the procedure are presented by an application to the variation of mean sea level in the northern Adriatic sea in the last century. The mean sea level in the region is found to be inhomogeneous both in time and space. The rate of increase in mean sea level is at some sites equal to that of the Mediterranean basin, which in turns equals the change in global mean sea level. At other sites, starting from about year 1950, the rate is one order of magnitude larger. The latter suggests soil compaction due to water draining from the water bearing table for agricultural use as the main active factor.

Sea-level trends and physical consequences: applications to the U.S. shore

As our knowledge of the potential for future global warming increases, our understanding of the imminent dangers associated with continued, possibly accelerated, sea-level rise increases. Several independent research groups have predicted future sea-level rise on the order of 15 to 50 cm by the middle of next century, and between 30 and 110 cm by 2100. Considering the concentration of coastal populations, and dollar value of industries and developments, these increases in mean sea level pose significant hazards. A linkage exists between sea-level history and climate history, but research has demonstrated that sea level is controlled by a complex interaction of geologic, hydrologic and climatologic factors. Because of insufficient data describing global-scale hydrological phenomena, we lack understanding of the components of sea-level change. Present estimates of the various contributions to trends in sea level do not agree with physical measurements of sea-level history. This hampers our ability to make accurate predictions of sea-level behavior. Sea-level rise implies the future threat of accelerated coastal erosion, increased frequency and severity of structural damage resulting from storms which make landfall, salinization of groundwater resources and estuarine and other aquatic ecosystems, destruction of coastal wetlands leading to severe impacts on coastal marine biologic communities, and significant damage to the infrastructure of coastal cities and other population centers. Federally sponsored study groups have completed a series of specific recommendations dealing with the threat of sea-level rise and appropriate responses by parties concerned with the coastal zone. These describe a policy of planned retreat from the coast on a schedule dictated by natural events and processes. The Federal Emergency Management Agency would delineate coastal hazard zones and provide appropriate planning policies governing future development. Compliance with hazard zone standards would determine landowner participation in the National Flood Insurance Program. Federal, state, local and private interests in coastal lands should respond to the threat of sea-level rise and coastal erosion with innovative land management policies and practices that encourage the establishment of coastal high-risk zones and conversion of these lands to low-risk usage.