DARSea: Detection and Attribution of 20th century Regional Sea-level change

Global mean sea level has been rising at a rate of 1.7 (1.3-2.1) mm/yr since 1900, increasing to 3.3 (2.9-3.6) mm/yr for the period 1993-2018. However, from satellite altimetry observations we know that regional changes can be up to three times faster than the global mean. It is precisely this regional sea-level change which matters to coastal societies when they are deciding on defensive and adaptive measures. Unfortunately, the drivers of regional sea- level changes in the 20th century are not accurately known yet. Therefore, there is an urgent need to reconstruct 20th century regional sea-level changes, such that we can unravel its causes and determine the part of the observed changes that is driven by man-made greenhouse gas emissions.
In this Vidi project, we use improved observations and state-of-the-art models to reconstruct regional sea-level change for the 20th century. We take a budget approach, in which we compare the sum of individual contributions to sea-level change with the total change. To maximise the chances of closure of the sea-level budget on the finest possible spatial scale, we will use machine learning techniques to find regions with coherent sea-level variability. The observational and simulated regional sea-level budgets will be used to answer the following three main research questions: (i) how well do models simulate observed regional sea-level change? (ii) can we close the 20th century regional sea-level budget? and (iii) which part of the regional observed changes can we attribute to man-made and natural drivers?
The answers to these questions will help coastal societies to understand why the sea level has changed along their coast and which part is caused by man-made climate change. This knowledge will allow policymakers to make well-informed decisions on coastal protection against future sea-level rise.