Secular changes in Earth’s shape and surface mass loading derived from combinations of reprocessed global GPS networks

Abstract

The changing distribution of surface mass (oceans, atmospheric pressure, continental water storage, groundwater, lakes, snow and ice) causes detectable changes in the shape of the solid Earth, on time scales ranging from hours to millennia. Transient changes in the Earth's shape can, regardless of cause, be readily separated from steady secular variation in surface mass loading, but other secular changes due to plate tectonics and glacial isostatic adjustment (GIA) cannot. We estimate secular station velocities from almost 11 years of high quality combined GPS position solutions (GPS weeks 1,000-1,570) submitted as part of the first international global navigation satellite system service reprocessing campaign. Individual station velocities are estimated as a linear fit, paying careful attention to outliers and offsets. We remove a suite of a priori GIA models, each with an associated set of plate tectonic Euler vectors estimated by us; the latter are shown to be insensitive to the a priori GIA model. From the coordinate time series residuals after removing the GIA models and corresponding plate tectonic velocities, we use mass-conserving continental basis functions to estimate surface mass loading including the secular term. The different GIA models lead to significant differences in the estimates of loading in selected regions. Although our loading estimates are broadly comparable with independent estimates from other satellite missions, their range highlights the need for better, more robust GIA models that incorporate 3D Earth structure and accurately represent 3D surface displacements.

CARIB18: A Stable Geodetic Reference Frame for Geological Hazard Monitoring in the Caribbean Region

“…A stable reference frame indicates that regional "common" movements have been removed or minimized. The regional common movements may include a combination of secular plate motions, glacial isostatic adjustment, surface mass loading, and other minor secular effects [32].…”

Rapid Prediction of Vertical Deflections and Their Statistics for Surveying and Mapping Applications: Three Case Studies

“…This concept of adding secular contributions to the velocities of points on the earth's surface is not new. Recently Booker et al (2014) entertained this idea writing explicitly: "The secular motion of any point on the earth will be a combination of GIA, plate tectonics, present-day surface mass loading, and other secular effects which we here assume to be negligible." Clearly, the secular motion of the frame itself as described herein could be another contribution not to be discarded.…”