Contributions of thermal expansion of monuments and nearby bedrock to observed GPS height changes

Long-term continuous Global Positioning System (GPS) observations have become an important tool for studying the various geodynamic processes. To fully study the geodynamic processes at GPS stations, the temporal movements of GPS monuments and nearby bedrock induced by thermal expansion need to be considered. In this paper, we extend a theoretical model to estimate the thermal expansions of GPS monuments and nearby bedrock for 86 globally distributed GPS stations based upon measurements of surface air temperatures. The results show that annual temperature variations are the dominant contributors for the thermal expansion of GPS monuments and nearby bedrock. The contributions of thermal expansion to GPS height changes display largely spatial variations and can reach to a few millimeters.