Causes of Decadal to Centennial Regional Sea Level Variations (DECVAR-2)

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During the first phase of the SPP 1889 SeaLevel we investigated processes related to the impact of various forcing mechanisms on sea level projections as well as statistical properties of natural sea level variations along coastlines. Results are important to understand primary forcing components, regions where the forcing is most efficient as well as the way different models react to the same forcing thereby spanning an uncertainty range of model projections. Continuing this work, we will bring it to full fruition by focusing on future decadal and long-term regional sea level variations from basin scale down to local scale around the two SPP study regions, notably the western tropical Pacific and Indonesian through-flow region as well as the German Bight. For a better understanding of future sea level changes on decadal to centennial time-scales in terms of natural dynamic modes versus anthropogenic influences, it is important to identify potential underlying forcing factors as well as natural dynamical contributions which includes coastal dynamics. Our study will be based on a spectrum of numerical simulations, aided by observations to evaluate them. By jointly analyzing these results, the study aims at identifying causes for future regional to local sea level variations taking into account free (natural) climate modes as well as external forcing mechanisms, including anthropogenic forcing. DECVAR-2 is part of the SPP 1889 focus group on global to regional sea level variations and will also contribute sea level change information to the other focus groups with respect to sea level anomalies in the western tropical Pacific and ITF region as well as in the eastern North Atlantic with focus on the German Bight. Within the focus group on global to regional sea level variations the project will provide global sea level simulation and projections including knowledge about forcing mechanism for naturally and anthropogenically forced changes. As the only global sea level modeling approach it will attribute projected changes to different forcing mechanisms and provide a global context for regional sea level variability. Answers provided will be essential to reach the overarching SPP goals in the sense that process information will be provided affecting sea level on regional to local spatial scale that will enable projections or predictions in coastal areas. This information will be extremely important for future coastal management in the study regions and will form the basis for a better-informed planning of adaptation measures. It will also be essential to improve our understanding of sea level predictability in various parts of the world.