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Nonlinear subsidence at Fremantle, a long‐recording tide gauge in the Southern Hemisphere
Author(s) -
Featherstone W. E.,
Pen. T.,
Filmer M. S.,
Williams S. D. P.
Publication year - 2015
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2015jc011295
Subject(s) - global positioning system , subsidence , geodetic datum , geodesy , geology , tide gauge , post glacial rebound , track (disk drive) , sea level , structural basin , acceleration , northern hemisphere , geomorphology , climatology , oceanography , engineering , telecommunications , mechanical engineering , physics , classical mechanics
A combination of independent evidence (continuous GPS, repeat geodetic leveling, groundwater abstraction, satellite altimetry, and tide gauge (TG) records) shows that the long‐recording Fremantle TG has been subsiding in a nonlinear way since the mid‐1970s due to time‐variable groundwater abstraction. The vertical land motion (VLM) rates vary from approximately −2 to −4 mm/yr (i.e., subsidence), thus producing a small apparent acceleration in mean sea level computed from the Fremantle TG records. We exemplify that GPS‐derived VLM must be geodetically connected to the TG to eliminate the commonly used assumption that there is no differential VLM when the GPS is not colocated with the TG. In the Perth Basin, we show that groundwater abstraction can be used as a diagnostic tool for identifying nonlinear VLM that is not evident in GPS time series alone.