Sources of 21st century regional sea-level rise along the coast of northwest Europe

[摘要] Changes in both global and regional mean sea level, and changes in themagnitude of extreme flood heights, are the result of a combination ofseveral distinct contributions most, but not all, of which are associatedwith climate change. These contributions include effects in the solid earth,gravity field, changes in ocean mass due to ice loss from ice sheets andglaciers, thermal expansion, alterations in ocean circulation driven byclimate change and changing freshwater fluxes, and the intensity of stormsurges. Due to the diverse range of models required to simulate thesesystems, the contributions to sea-level change have usually been discussedin isolation rather than in one self-consistent assessment. Focusing on thecoastline of northwest Europe, we consider all the processes mentionedabove and their relative impact on 21st century regional mean sealevels and the 50-year return flood height. As far as possible ourprojections of change are derived from process-based models forced by theA1B emissions scenario to provide a self-consistent comparison of thecontributions. We address uncertainty by considering both a mid-range and anillustrative high-end combination of the different components.

For our mid-range ice loss scenario we find that thermal expansion ofseawater is the dominant contributor to change in northwest European sealevel by 2100. However, the projected contribution to extreme sea level, dueto changes in storminess alone, is in some places significant and comparableto the global mean contribution of thermal expansion. For example, under theA1B emissions scenario, by 2100, change in storminess contributes around15 cm to the increase in projected height of the 50-year storm surge on thewest coast of the Jutland Peninsula, compared with a contribution of around22 cm due to thermal expansion and a total of 58 cm from all of thecontributions we consider. An illustrative combination of our high-endprojections suggests increases in the 50-year return level of 86 cm atSheerness, 95 cm at Roscoff, 106 cm at Esbjerg, and 67cm at Bergen. Thenotable regional differences between these locations arise primarily fromdifferences in the rates of vertical land movement and changes instorminess.

[学科分类] 海洋学与技术