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

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

Here and now: perceptions of Indian Ocean islanders on the climate change and migration nexus

Empirical studies exploring the links between climate change and migration are increasing. Often, perceptions are not fully explored from the people most affected by the climate change and migration nexus. This article contributes to filling this gap by eliciting and analyzing perceptions regarding climate change and migration from an understudied population labelled as being amongst those most immediately and directly affected by climate change: Indian Ocean islanders. Open-ended, semi-structured interviews were conducted in two case study communities in Maldives (Kaafu Guraidhoo with 17 interviews and Raa Dhuvafaaru with 18 interviews) and two case study communities in Lakshadweep, India (Kavaratti with 35 interviews and Minicoy with 26 interviews). The results present the interviewees’ perceptions of climatic variability and change that they experience; how they perceive the causes of these changes; and links to migration decisions. The interviews demonstrate that perceptions of climate change, of migration, and of the links or lack thereof between the two are centred on the interviewees’ own experiences, their own locations, and the immediate timeframe. External information and direction has limited influence. Their perceptions are framed as being the ‘here and now’ through topophilia (here) and tempophilia (now). The islanders’ views do not avoid, but rather encompass, long-term livelihoods and the future. Such a future might be in another location, but the anchor is expressing future hopes and aspirations through the here and now. It is not linked to the wide-scale, long-term issue of climate change

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

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