This study seeks to contribute to the fundamental question of how climate change influences the ocean over periods of decades to centuries, and how these variations in relative sea level are manifested in coastal sedimentary sequences. From this work a common taxonomic basis and ecological data set of marsh foraminifera has been achieved for the western and northern coasts of the Iberian Peninsula. It was also provided the first quantitative, high-resolution, study of the sea level for the east coast of the North Atlantic.