Mean sea level studies from tide gauge and satellite altimetry time series looking for the integration of Brazilian Vertical Network to SIRGAS

In Geodesy, the monitoring of sea level plays an important role in the realization of global reference systems and allows the integration of available data from classical vertical networks, whose Vertical Datum is usually defined by the Mean Sea Level (MSL), with different periods of observation and related to a specific epoch. The fact that each vertical datum is related to a defined epoch (the sea level is variable in space and time) associated with the leveling errors, produces significant differences in heights referred to different vertical nets; that shows the importance of the sea level monitoring. Usually, efforts must be done to recover old information and data. In this work, the main aspects related to the Brazilian Vertical Datum (BVD), its time evolution and the search of alternatives to determine this evolution are presented. Preliminary results, based in tide gauge and leveling data, have shown an increasing of the MSL at Imbituba harbor of about 2 mm/a, in the integration of time series stored at Permanent Service for Mean Sea Level (PSMSL) with recent digital data. This agrees with results of global sea level changes. Nowadays, satellite altimetry is an efficient way to monitor MSL variations. In this paper, are presented some results related with the comparison of satellite altimetry data and longer tide gauge temporal series, as those for Cananéia and Ilha Fiscal tide gauges, whose correlation coefficients are better than 0.8 among the series, in order to establish analysis methods applicable to BVD region.