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

Abstract. A coastal sea level reconstruction based on tide gauge
observations is developed and applied to the western basin of the
Mediterranean sea. The reconstructions are carried out in four frequency
bands and are based on an optimal interpolation method in which the
correlation between tide gauge data and all coastal points has been
determined from the outputs of a numerical model. The reconstructions for
frequencies 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 of
higher frequencies, hourly observations from the Global Extreme Sea Level
Analysis (GESLA-2) dataset are used
and cover from 1980 to 2015. Total sea level is retrieved with high accuracy
from the merging of the different frequency bands. Results of a
cross-validation test show that independent tide gauge series are highly
correlated with the reconstructions. Moreover, they correlate significantly
better with the reconstructions than with altimetry data in all frequency
bands, and therefore the reconstruction represents a valuable contribution
to the attempts of recovering coastal sea level. The obtained
reconstructions allow us to characterize the coastal sea level variability,
estimate coastal sea level trends along the entire coastline, and examine
the correlation between western Mediterranean coastal sea level and the main
North Atlantic climate indices. The limitations and applicability of the
method to other regions are also discussed.
