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The coastal zone is an area of high interest, characterized by increased population density, hosting important commercial activities and constituting habitats of high socioeconomic value (Costanza 1999). Sea level rise (SLR) in view of climate change poses a serious threat to coastal areas and as a consequence, much research effort has focused on this aspect of coastal hazard (Church and White 2011; Hinkel et al. 2014; Hogarth 2014; Hoggart et al. 2014; Jevrejeva et al. 2014; Losada et al. 2013; Tol 2009). Extreme events, however, determine an additional hazard component. Some studies report an increased intensity and frequency of extreme water levels along several coastal regions in the world (Izaguirre et al. 2013; Ullmann and Monbaliu 2010; Wang et al. 2014; Weisse et al. 2014). However, the majority of the observed changes are related to changes in mean sea level (Menéndez and Woodworth 2010), while there is a lack of significant trends in storminess (Dangendorf et al. 2014a; Woodworth and Blackman 2002). The latter is in agreement to the conclusions of Ferreira et al. (2009), who found no statistically significant increasing.
Storm surges, also referred to as meteorological residuals or meteorological tide, constitute along with the waves and the tidal oscillations the main components of extreme water levels along the coastal zone (Losada et al. 2013; Lowe et al. 2010). Storm surges are forced by wind driven water circulation towards or away from the coast and by atmospheric pressure driven changes of the water level; i.e. the inverse barometric effect (WMO 2011). The magnitude of the storm surge depends on a number of factors including the size, track, speed and intensity of the storm system, the nearshore local bathymetry (water depth) and the shape of the coastline (Arns et al. 2015).
The estimated extreme SSL obtained by the 8-member model ensemble appeared to follow similar spatial patterns among the different scenarios and return periods (Fig. below); with SSL values along the North Sea increasing eastwards, and being substantially higher than the ones along the rest of Europe. Another area characterized by higher SSL values was the UK coastline of the Irish Sea, followed by marginal areas of the Baltic Sea (e.g. Kattegat, Gulf of Finland and the North Gulf of Bothnia; see Fig. below) and the Norwegian Sea. Anticipated extreme SSL appeared to be η s < 2 m for most of South Europe with higher values observed along parts of the North Adriatic and of the North Black Sea.
The North Sea was projected to experience increased storm surge activity (Fig. below), especially towards the end of the century, i.e. the present 100-year event was projected to occur every 80.2 and 81.3 years under RCP4.52100 and RCP8.52100, respectively. The relative change in extreme SSL was shown to increase eastwards, as most of the UK east coast showed small decrease or no change . Strong projected increase in frequency was also observed for the Baltic Sea, for all scenarios apart from RCP4.52040; with the present day 100-year event projected to take place every 44, 72, and 51 years under RCP8.52040, RCP4.52100, and RCP8.52100, respectively. Finally an increase in storm surge intensity was projected for the Norwegian Sea for all RCPs, with the present day 100-year event projected to take place every 79.4, 51, 63.5, and 47.7 years under RCP4.52040,RCP8.52040, RCP4.52100, and RCP8.52100, respectively
Ensemble mean of extreme SSL (m) along the European coastline obtained for 5, 10, 50, and 100 years return periods (shown in different columns), for the baseline period (a–d), as well as their projected relative changes under RCP4.52040 (e–h), RCP8.52040 (i–l), RCP4.52100 (m–p), RCP8.52100 (q–t) scenarios (shown in different lines). Warm/cold colors express increase/decrease, respectively; while points with high model disagreement are shown with gray (|CV| > 1)
Overview of changes in the extreme SSL along the 10 defined European regions (a–j): horizontal axis expresses return period in years and the vertical the corresponding SSL, while each curve corresponds to a different RCP scenario and time slice: baseline (red), RCP4.52040 (blue), RCP8.52040 (green), RCP4.52100 (purple), RCP8.52100 (orange). The inset map (k) shows the limits of the 10 European regions
from https://link.springer.com/article/10...382-016-3019-5
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