Sea level rise (and in some places, sea level fall) is one of the most troublesome of ongoing environmental changes, with potential and likely impacts generating huge costs for inevitable adaptation. Despite a growing literature discussing past, present and future sea level shifts, quantitative understanding of the causes of both regional and global mean sea level change remains quite poor?because the shifts reflect some of the most basic elements of physical oceanography, geodesy, glaciology, and meteorology, including biases from inadequate and shifting observation systems and small but accumulating errors in ocean models. Almost all of the resulting issues are discussed somewhere in the voluminous and growing literature, but primarily in isolation. The intent of this project is to combine into one framework, that of a specially adapted ocean general circulation model and all of the available data, to quantify the causes of regional and global sea levelchange. Separate, but overlapping efforts would be directed to the period(s) since 1992, and the much more data sparse periods prior to that time.
Intellectual Merit: Understanding of the components, spatial distribution and rates of sea level rise has enormous social consequences. A sea level rise of 1 mm per year versus one of 4 mm per year sustained for 25 years implies adaptation costs that differ by orders of magnitude. Observed regional rates of change, which are the ones of societal importance, are more than an order of magnitude greater and of both signs.
Broader Impacts: At the present time one cannot make credible predictions, and this work should take a major step toward that goal. Impacts and adaptation strategies are not part of this proposal, but it should be of interest to anyone concerned about those problems.
