Ocean acidification in shelf seas: impact of large-scale forcing and local dynamics

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We present the result of a 60-year hindcast simulation from the model ECOSMO II in the North Sea andBaltic Sea in terms of pH in the upper 50 m. A general decrease of pH is reproduced, with differentacidification rates depending on the basin. The Baltic seems to acidify at a slower rate than the North Sea.Various potential drivers behind this heterogeneity have been explored: the atmospheric increase in CO2is clearly the main forcing or the acidification, although its correlation with the North Sea pH is strongerthan the Baltic. Climate indices, primary production, and water temperature correlate differently, or not atall, with each basin, showing that each system has its own processes that modulate the main pH signal.