81 research outputs found

    Changes in wave climate over the northwest European shelf seas during the last 12,000 years

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    Because of the depth attenuation of wave orbital velocity, wave-induced bed shear stress is much more sensitive to changes in total water depth than tidal-induced bed shear stress. The ratio between wave- and tidal-induced bed shear stress in many shelf sea regions has varied considerably over the recent geological past because of combined eustatic changes in sea level and isostatic adjustment. In order to capture the high-frequency nature of wind events, a two-dimensional spectral wave model is here applied at high temporal resolution to time slices from 12 ka BP to present using paleobathymetries of the NW European shelf seas. By contrasting paleowave climates and bed shear stress distributions with present-day conditions, the model results demonstrate that, in regions of the shelf seas that remained wet continuously over the last 12,000 years, annual root-mean-square (rms) and peak wave heights increased from 12 ka BP to present. This increase in wave height was accompanied by a large reduction in the annual rms wave- induced bed shear stress, primarily caused by a reduction in the magnitude of wave orbital velocity penetrating to the bed for increasing relative sea level. In regions of the shelf seas which remained wet over the last 12,000 years, the annual mean ratio of wave- to (M-2) tidal-induced bed shear stress decreased from 1 (at 12 ka BP) to its present-day value of 0.5. Therefore compared to present- day conditions, waves had a more important contribution to large-scale sediment transport processes in the Celtic Sea and the northwestern North Sea at 12 ka BP

    Climate Change Impacts on the Mediterranean Coastal Zones

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    Vulnerability of the Netherlands and NW Europe to storm damage under climate change

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    Storms occasionally bring havoc to Northwest Europe. At present, a single storm may cause damage of up to 7 billion U.S.$, of which a substantial part is insured. One scenario of climate change indicates that storm intensity in Northwest Europe could increase by 1-9% because of the doubling of CO2 concentrations in the atmosphere. A geographic-explicit, statistical model, based on recent storms and storm damage data for the Netherlands, shows that an increase of 2% in wind intensity by the year 2015 could lead to a 50% increase in storm damage to houses and businesses. Only 20% of the increase is due to population and economic growth. A 6% increase could even triple the damage. A simpler model - based on national average data and combined with a stochastic storm generator - shows that the average annual damage could increase by 80% with a 2% increase in wind intensity. A 6% wind intensity increase could lead to an average annual damage increase of 500%. The damage in Northwest Europe is about a factor 6 higher than the damage in the Netherlands. Little potential seems to exist for reducing the vulnerability to storms in the Netherlands. More attention should be given to planning at the government level for disaster relief and to the development of coping strategies
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