Reconstruction of Mediterranean coastal sea level at different timescalesbased on tide gauge records

A coastal sea level reconstruction based on tide gaugeobservations is developed and applied to the western basin of theMediterranean sea. The reconstructions are carried out in four frequencybands and are based on an optimal interpolation method in which thecorrelation between tide gauge data and all coastal points has beendetermined from the outputs of a numerical model. The reconstructions forfrequencies lower than 1 month use monthly observations from the Permanent Service for Mean Sea Level (PSMSL)database and cover the period from 1884 to 2019. For the reconstruction ofhigher frequencies, hourly observations from the Global Extreme Sea LevelAnalysis (GESLA-2) dataset are usedand cover from 1980 to 2015. Total sea level is retrieved with high accuracyfrom the merging of the different frequency bands. Results of across-validation test show that independent tide gauge series are highlycorrelated with the reconstructions. Moreover, they correlate significantlybetter with the reconstructions than with altimetry data in all frequencybands, and therefore the reconstruction represents a valuable contributionto the attempts of recovering coastal sea level. The obtainedreconstructions allow us to characterize the coastal sea level variability,estimate coastal sea level trends along the entire coastline, and examinethe correlation between western Mediterranean coastal sea level and the mainNorth Atlantic climate indices. The limitations and applicability of themethod to other regions are also discussed.