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The central north shore of Prince Edward Island comprises embayments separated by subtle headlands that may constrain nearshore sediment transport. The study area includes two such embayments informally known as Brackley and Tracadie bights, both of which are sand-rich onshore and sand-starved between 20 and 50 m water depth. Storm winds and waves from the northwest and northeast are common in autumn and winter. The hydrodynamic model Delft3D is used to simulate waves, currents, water levels, and sediment transport in Brackley and Tracadie bights during 23 autumn seasons between 1955 and 2005. When compared with wave and current measurements from a field experiment in the autumn of 1999, the model successfully simulates conditions during storms and fair-weather periods. Results from the simulations show that, in autumn, the weighted mean direction of transport is to the southeast (133°). Bedload transport is directed onshore to the south (170°), and suspended load is directed offshore to the northeast (67°). When aggregated over the 23 seasons, transport magnitudes and directions differ between Brackley and Tracadie bights. Rates of transport are higher in Tracadie Bight and directed more to the east. During individual storms, transport is dependent on the storm wind and wave direction. Most transport occurs in bed load, and deposition occurs at the shoreline, with erosion offshore. The patterns of bed load and suspended load suggest a mechanism for the landward migration of this shoreline during transgression, and may explain the existence of the sand-starved zone offshore. [ABSTRACT FROM AUTHOR]

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Changes to the Beaufort Sea shoreline occur due to the impact of storms and rising relative sea level. During the open-water season (June to October), storm winds predominantly from the north-west generate waves and storm surges which are effective in eroding thawing ice-rich cliffs and causing overwash of gravel beaches. Climate change is expected to be enhanced in Arctic regions relative to the global mean and include accelerated sea-level rise, more frequent extreme storm winds, more frequent and extreme storm surge flooding, decreased sea-ice extent, more frequent and higher waves, and increased temperatures. We investigate historical records of wind speeds and directions, water levels, sea-ice extent and temperature to identify variability in past forcing and use the Canadian Global Coupled Model ensembles 1 and 2 (CGCM1 and CGCM2) climate modelling results to develop a scenario forcing future change of Beaufort Sea shorelines. This scenario and future return periods of peak storm wind speeds and water levels likely indicate increased forcing of coastal change during the next century resulting in increased rates of cliff erosion and beach migration, and more extreme flooding.[Traduit par la rédaction] Des changements dans la ligne de rivage de la mer de Beaufort se produisent sous l'effet des tempêtes et de la hausse relative du niveau de la mer. Durant la saison d'eau libre (de juin à octobre), les vents des tempêtes, principalement du nord-ouest, produisent des vagues et des marées de tempêtes qui parviennent à éroder les falaises riches en glace fondante et à produire un ennoiement des plages de gravier. On s'attend à ce que le changement climatique soit accentué dans les régions arctiques par rapport à la moyenne globale et qu'il entraîne une hausse accélérée du niveau de la mer, des vents de tempêtes extrêmes plus fréquents, des inondations causées par des marées de tempêtes plus fréquentes et plus extrêmes, une plus faible étendue de la glace de mer, des vagues plus fréquentes et plus hautes et des températures plus élevées. Nous étudions les relevés historiques de vitesse et de direction du vent, de niveaux d'eau, d'étendue de la glace de mer et de température pour déterminer la variabilité dans le forçage passé et nous utilisons les résultats de modélisation du climat des modèles couplés climatiques globaux 1 et 2 (MCCG1 et MCCG2) pour élaborer un scénario forçant le changement futur des lignes de rivages de la mer de Beaufort. Ce scénario et les périodes de retour futures des vitesses de vent de tempête et des niveaux d'eau de pointe indiquent selon toute probabilité un forçage accru du changement côtier durant le prochain siècle produisant de plus forts taux d'érosion des falaises et de migration des plages ainsi que des inondations plus extrêmes. [ABSTRACT FROM AUTHOR]

Storms play a major role in shoreline recession on transgressive coasts. In the southern Gulf of St. Lawrence (GSL), southeastern Canada, long-term relative sea-level rise off the North Shore of Prince Edward Island has averaged 0.3 m/century over the past 6000 years (>0.2 m/century over 2000 years). This has driven long-term coastal retreat at mean rates >0.5 m/a but the variance and details of coastal profile response remain poorly understood. Despite extensive sandy shores, sediment supply is limited and sand is transferred landward into multidecadal to century-scale storage in coastal dunes, barrier washover deposits, and flood-tidal delta sinks. Charlottetown tide-gauge records show mean relative sea-level rise of 3.2 mm/a (0.32 m/century) since 1911. A further rise of 0.7±0.4 m is projected over the next 100 years. When differenced from tidal predictions, the water-level data provide a 90-year record of storm-surge occurrence. Combined with wind, wave hindcast, and sea-ice data, this provides a catalogue of potentially significant coastal storms. We also document coastal impacts from three recent storms of great severity in January and October 2000 and November 2001. Digital photogrammetry (1935–1990) and shore-zone surveys (1989–2001) show large spatial and temporal variance in coastal recession rates, weakly correlated with the storm record, in part because of wave suppression or coastal protection by sea ice. Large storms cause rapid erosion from which recovery depends in part on local sand supply, but barrier volume may be conserved by washover deposition. Barrier shores with dunes show high longshore and interdecadal variance, with extensive multidecadal healing of former inlet and overwash gaps. This reflects recovery from an episode of widespread overwash prior to 1935, possibly initiated by intense storms or groups of storms in the latter half of the 19th century. With evidence from the storms of 2000–2001, this points to the importance of storm clustering on scales of weeks to years in determining erosion vulnerability, as well as the need for a long-term, large-scale perspective in assessing coastal stability. The expected acceleration in relative sea-level rise, together with projections of increasing storm intensity and greatly diminished winter ice cover in the southern GSL, implies a significant increase in coastal erosion hazards in future. [Copyright &y& Elsevier]