Extension of high temporal resolution sea level time series at Socoa (Saint Jean-de-Luz, France) back to 1875

Abstract. In this data paper sea level time series at Socoa (Saint Jean-de-Luz, Southwestern France) is extended in a data archaeology exercise. We have catalogued water level records stored in ledgers and charts, as well as other associated documents (metadata) in thorough research of national and local archives. An extensive effort was made to rescue these documents by archiving them in digital formats. Based on this large set of rescued documents, the Socoa time series is further extended back in time by about 40 years, at hourly (for ledgers) to 5-minutes (for charts) sampling. Analysis of the precise levelling information reveals that the datum of the tide gauge site has been stable. We assessed the consistency of this new century-long time series based on nearby tide gauge data. Although the overall timeseries is generally consistent, siltation is found to be a recurrent problem of the stilling well which impacted some part of the extended data. However, being a high temporal resolution sea level time series spanning more than 100 years, this new dataset will be useful for advancing climate research, particularly the decadal scale variations in the North Atlantic, as well as the storminess and extreme events along the French Basque coastal region.