Understanding sea level rise using polar motion from 1979 to 2

Sea level rise is one of the most significant consequences of the warming climate. GRACE and GRACE Follow-On satellites have been providing critical clues about the primary contributor to recent sea level rise, such as the melting ice sheets and mountain glaciers, and the depletion of terrestrial water storage. However, due to the limited availability of satellite gravity data (only since 2002) and other direct observations, understanding changes in ocean mass during the 20th century had to rely on global hydrological or Earth systems modeling. On the other hand, efforts have been made to understand the past sea level rise using a combination of optical/microwave satellite imagery of polar regions, along with glaciological and geodetic data for mountain glaciers, global databases for large dams, and climate models for terrestrial water storage. Despite these efforts, verifying the accuracy of the combined estimates requires independent long-term observational evidence. In this presentation, we show that studying Earth’s polar motion presents a unique opportunity to comprehend historical sea level rises predating the GRACE satellite era. Observed polar motion data from 1979 to 2010 agree well with estimates derived from various observations and climate models. During this period, the total increase in ocean mass is estimated to 52.94 mm (equivalent to 1.65 mm per year), encompassing contributions from ice melting in Antarctica (9.11 mm), Greenland (8.95 mm), mountain glaciers (20.16 mm), and the depletion of terrestrial water storage (13.72 mm). This approach utilizing polar motion offers a valuable means for historical sea level rise assessments, filling gaps in our understanding before the advent of the GRACE satellite missions.