University of Montana, Maureen and Mike Mansfield Library
Abstract
Surface mass loading contributes a ubiquitous signal to GPS time series that can be modeled and removed for individual sources. We utilize nine GPS stations in the Susitna River watershed, Alaska, to investigate surface displacements from surface mass loading. We find that modeling atmospheric surface pressure and regional hydrologic mass reduces root mean square (RMS) error by 27-39% for all GPS time series. We observe moderate correlation between residual time series pairs and distance, with elevation differences influencing the strength of this correlation. Seasonal horizontal and vertical displacements are observed after removal of all loading models; stations displace downward and northwest during winter months, and upward and southeast during summer months. The temporal displacements are generally correlated with precipitation and Susitna River discharge. Removing the common mode error (CME) from all stations highlights small variations in both spatial and temporal displacements, with time series reflecting local loading sources rather than being dominated by regional trends. The standard deviation of the post-CME measurements indicates that there is moderate uncertainty in both phase and amplitude information. GPS measurement uncertainties contribute to the standard deviation, as well as inter-annual variations in climate; stations also deform due to local variations in temperature and precipitation
