**8. Summary and prospects**

The sea level is a key variable of the climate system. Tide gauges measuring sea level variability are in operation since the 1900s. Satellite-based observations of sea level changes are more recent. Nevertheless, they play a crucial role in understanding the future coastal sea level changes. Advance in the processing of satellite radar altimetry have expanded the utility of this data set for climate-related studies and extended the potential exploitation in the coastal zone. The joint usage of the two different measuring systems (in situ and satellite) has two challenges. First how the two data sets can be consistently and systematically used in synergy to address that objective of estimating robust coastal sea level trends. Second how using high-rate (i.e. 20 Hz) altimeter measurements with a coastal-oriented processing could improve the satellite-based trend estimates with respect to the standard (1 Hz) data, especially near coast.

In this chapter, a more robust inverse method (called LIPWC-COV) has been proposed and tested in the Northern Adriatic Sea, where GPS data are available to conduct a realistic assessment of uncertainties. The results show that the classical approach of estimating VLMs provides less accurate trends than the LIPWC-COV method, and with lower errors. Moreover, the LIPWC-COV has demonstrated to compare better than the classic method with GPS derived VLMs.

In this chapter, the experimental SLCCI data set (high resolution along track) coastal sea level product (developed within SLCCI project) has been also assessed in the Gulf of Trieste, as it was possible only at that site. The retrieval is particularly problematic in the gulf area due to the complex morphology of the land. The trends calculated with the gridded and along track datasets show some differences, probably due to the different methodologies used in the generation of the products.

This study offers a more consolidated and improved understanding of the sea level trend variability in the Northern Adriatic Sea. The next step is to extend the application of the new methodology to the Mediterranean Sea.
