One important result is depicted in Figure 18. The higher see more temperature gradient of ‘2 × CO2’ causes a stronger cyclonic circulation and, as a consequence of the geostrophic balance, a higher mean water level up to 24 cm in the southern North Sea. On top of this, the global isostatic water level rise must be added. The regional wind forcing from the ‘2 × CO2’ scenario has been used by Langenberg et al. (1999) to study storm-related sea level variations along the North Sea coast. The result is summarized for eight locations on the Dutch–German–Danish coast (Figure 19). The mean storm surge levels (50% percentile) rise significantly

along the whole coastal section, but the extremes (90% percentile) do not exceed the statistical noise. The conclusion is that higher surges learn more will be faced but no new extremes. Jungclaus & Wagner (1988) have investigated the gradual alteration of the M2-tide in the North Sea as a consequence of the global rise in mean sea level. They applied a two-dimensional barotropic model to the cases of 2, 5 and 10 m rises. The variations are not dramatic, but nevertheless clear in tendency. The central amphidromic point in the southern North Sea (see Figure 2) is gradually shifting (as theoretically expected) towards the north-west. Within

the next 100 years this will cause a slight growth of tidal ranges on the German, Danish and Norwegian coasts and a slight decrease in Dutch and British waters (Figure 20). At the International North Sea conferences in Hamburg (1996) and in Wilhelmshaven (2000) ‘Grand Challenges’ for North Sea research were formulated (Sündermann et al. 2001): • The interactions between the north-west European shelf and its adjacent oceanic and terrestrial regimes, i.e. with the North

Atlantic and the European landmass. This topic has particular relevance to questions on climate change and its effects on the North Sea ecosystem. These challenges lead, of course, beyond physics and concern all the marine sciences, as well as coastal engineering, socio-economics and politics. For marine physics the following research areas can be highlighted (Sündermann 2003a): The transfer mechanisms of Atlantic variability to the North Sea have to be analysed and quantified. Methocarbamol This concerns both the physical and the biological subsystems, and encompasses time scales from seasons to decades. Of specific interest is the causal chain of global climate change – the reaction of the marine ecosystem to bentho-pelagic coupling and changes in biodiversity. Key processes include upper layer dynamics, eutrophication, algal blooms, dynamics of pollutants, trophic relations, recruitment, morphodynamics, pelago-benthic coupling, nutrient regeneration and biodiversity. Targeted process-oriented field experiments should be combined with laboratory work (incl. mesocosms) and model investigations.