The Sea Level Fingerprints of Global Terrestrial Water Storage Changes Detected by GRACE and GRACE-FO Data

The climate-related melting of ice sheets and glaciers and the human-related redistribution of terrestrial water altered the Earth's gravity and displacement field and resulted in non-uniform sea level changes, i.e., sea level fingerprints (SLF). Satellite gravity is an important approach in monitoring the spatio-temporal evolution process of global terrestrial water storage (TWS) and its relevance to sea level changes. This study uses the mascon (mass concentration) product of Gravity Recovery and Climate Experiment (GRACE) and its Follow-on (GRACE-FO) to estimate the global TWS changes from 2002 to 2020. Subsequently, the global SLF caused by the redistribution of land and sea water mass is calculated based on the sea level equation, which includes both the self-attraction effect of loads and the feedback effect of the Earth's polar motion. Based on the results, the global TWS showed a decreasing trend (- 740.98 +/- 41.64 Gt/year), with significant spatial differences. Consequently, the sea level maintained an upward trend (1.97 +/- 0.10 mm/year), exhibiting typical fingerprint characteristics. Considering the sea level change (1.08 +/- 0.10 mm/year) influenced by its steric variation, such as thermal expansion and salinity variation, we estimated that the total change rate of the global sea level is 3.05 +/- 0.10 mm/year. The positive contribution of terrestrial water roughly amounted to 2.58 times the negative contribution. The melting of polar ice masses primarily contributes to the global TWS loss and sea level rise (0.46 +/- 0.01 and 0.38 +/- 0.02 mm/year for Greenland and Antarctica, respectively, excluding the peripheral glaciers). Another major contribution to sea level rise in the melting of glaciers (0.85 +/- 0.01 mm/year, with the peripheral glaciers around Antarctica and Greenland). Furthermore, we found that the removal of coastline ice mass leads to the fingerprints effect, meaning that the relative sea level (RSL) does not increase but decreases around Greenland and Antarctica. Notably, the factors driving land-sea mass redistribution also include artificial reservoirs as well as groundwater and surface water, of which the latter has an overall smaller positive contribution (0.28 +/- 0.07 mm/year) to the sea level rise. The role of artificial reservoirs in slowing down the sea level rise (- 0.57 +/- 0.07 mm/year) cannot be ignored.

Automated summary

This study uses satellite gravity data to estimate global terrestrial water storage changes and sea level changes from 2002 to 2020, and highlights the significant contribution of polar ice melting to global sea level rise.