Estimation and Attribution of Horizontal Land Motion Measured by the Greenland GNSS Network

Abstract

Horizontal land motion, as observed by geodetic techniques such as Global Navigation Satellite Systems (GNSS), is generally dominated by tectonic plate movement. However, in regions that are currently or formerly glaciated, such as Greenland, the deformation of the solid Earth due to surface loading complicates the separation of tectonic and glacial signals. Greenland, in particular, exhibits continent-wide horizontal motion of about $23\text{mm/year}$ toward the northwest direction, as recorded in the ITRF reference frame by the Greenland GNSS Network (GNET). Credible estimates of Greenland's plate motion are currently lacking, which hinders the ability to isolate other geophysical contributions. To address this, we first quantify the horizontal crustal velocity due to elastic deformation from present-day ice mass changes. We then derive a new plate motion model for the North American Plate using 2891 GNSS stations (including 55 from GNET) and estimate an improved Euler pole position. After removing the effects of both contemporary ice loss and plate motion, the residual horizontal velocity at each GNET site is attributed to Glacial Isostatic Adjustment (GIA) processes. This refined data set provides critical input for future three-dimensional GIA modeling, enabling more accurate reconstructions of the deglaciation history, as well as better constraints on the solid Earth structure and mantle viscosity beneath Greenland and North America.