Vertical Land Motion at Tide Gauges Observed by GNSS: A New GFZ-TIGA Solution

Abstract

Long-term tide gauge records provide valuable insights to sea level variations but interpretation requires an accurate determination of associated vertical land motion. Within the Tide Gauge Benchmark Monitoring Pilot Project of the International GNSS Service dedicated reprocessing campaigns are performed for GNSS stations co-located with tide gauges. Based on 341 stations the GFZ contribution to the third TIGA reprocessing provides vertical land motion rates for 230 stations at or close to recently active tide gauges. GNSS station coordinate time series determined by using a network approach and a conventional time series analysis show mean repeatabilities of 2.9, 3.3, and 5.6 mm for north, east, and up coordinates. The derived vertical velocity pattern is analyzed but also compared to the ALTIGAPS and the ULR6a solutions showing mean differences of 0.04 mm yr−1 and −0.1 mm yr−1, respectively. By correcting tide gauge records available via PSMSL for the individual vertical station velocity including eventually velocity changes geocentric sea level changes are determined. Compared to AVISO’s multi-mission altimetric trend map a difference of −0.7 mm yr−1 is determined.