Plain Language Summary: Ground‐based Global Positioning System (GPS) receivers allow us to track subtle changes in the Earth's shape. In this study, we use GPS data on vertical land motion to measure the response of Antarctica's bedrock to the loading caused by present‐day changes in the ice sheets. We demonstrate that variations in snowfall over decades and subsequent Earth deformations, which appear as varying trends in the GPS‐recorded vertical position time series, influence these measurements. We focus on observations from the Transantarctic Mountains and show that these factors can lead to biased estimates of the Earth's response to long‐term changes in the ice sheets, dating back to the last glacial maximum around 20,000 years ago, unless decadal GPS data records are available
