Effects of long-term variability on projections of twenty-first century dynamic sea level

Abstract

How regional sea level will change in response to ocean dynamics is investigated by altering initial atmosphere and ocean conditions in model projections. Internal variability in the ocean is found to cause large differences in projected changes. Sea-level rise1 is one of the most pressing aspects of anthropogenic global warming with far-reaching consequences for coastal societies. However, sea-level rise did2,3,4,5,6,7 and will strongly vary from coast to coast8,9,10. Here we investigate the long-term internal variability effects on centennial projections of dynamic sea level (DSL), the local departure from the globally averaged sea level. A large ensemble of global warming integrations has been conducted with a climate model, where each realization was forced by identical CO2 increase but started from different atmospheric and oceanic initial conditions. In large parts of the mid- and high latitudes, the ensemble spread of the projected centennial DSL trends is of the same order of magnitude as the globally averaged steric sea-level rise, suggesting that internal variability cannot be ignored when assessing twenty-first-century DSL trends. The ensemble spread is considerably reduced in the mid- to high latitudes when only the atmospheric initial conditions differ while keeping the oceanic initial state identical; indicating that centennial DSL projections are strongly dependent on ocean initial conditions.

Cite this article

Bordbar, M., Martin, T., Latif, M. et al. Effects of long-term variability on projections of twenty-first century dynamic sea level. Nature Clim Change 5, 343–347 (2015). https://doi.org/10.1038/nclimate2569

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