New Study: Sea level rose only 4 inches during 20th century

A paper published today in the Journal of Geophysical Research reconstructs sea level observations over the 129 year period from 1880 to 2009 along the coast of southern Spain and finds the 20th century sea level rise to be only 1 mm per year, equivalent to 4 inches per century.

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 116, C12003, 10 PP., 2011
doi:10.1029/2011JC007558

The long sea level record at Cadiz (southern Spain) from 1880 to 2009

Key Points

• Archived historical sea level data were recovered
• A composite time series longer than 100 yrs was built using leveling information
• Sea level trends are consistent among nearby records in southern Spain

Marta Marcos et al

Mean sea level observations from an historical tide gauge located in Cadiz (Southern Spain) spanning the period 1880–1924 were recovered from national archives. Daily sea level averages stored in handwritten log books were digitized, quality controlled, and referred to the same benchmark. A careful analysis of all the high precision leveling surveys available in the area of the tide gauge enabled the establishment of a common datum with a modern record starting in 1961 from another tide gauge located only 2.5 km apart, with accuracy better than 5 mm. As a result, a consistent daily mean sea level record from 1880 to 2009 was constructed. The 20th century relative mean sea level rise in Cadiz is 0.7 ± 0.1 mm yr⁻¹, which becomes 1.0 ± 0.2 mm yr⁻¹ once corrected for vertical land movement with high precision GPS data, in agreement with nearby records. The analysis of the seasonal sea level cycle indicated that the amplitude of the annual cycle has increased during the 20th century. This work evidences the significance of sea level data rescue for present-day climate research.