Water Density Variations of the Aral Sea from GRACE and GRACE-FO Monthly Solutions

The Gravity Recovery and Climate Experiment (GRACE) and its successor, the GRACE Follow-On (GRACE-FO) gravity satellite missions, have been providing monthly gravity field solutions for almost 20 years, enabling a unique opportunity to monitor large-scale mass variation processes. The gravity anomaly time series for the Aral Sea region has been obtained for the period of April 2002 to January 2022. The method of determining the gravity anomaly time series from GRACE and GRACE-FO monthly solutions has been improved by considering the mass variations of the Caspian Sea. The gravity anomaly time series was then compared to water mass changes determined by considering variations in the salinity and temperature of seawater. Nevertheless, the tests suggest that improvements in correlation with such information might occur, although the relevance of the improvement should not be overestimated. All in all, it can be demonstrated that salinity changes relevantly influence the gravity field; however, the signal is too weak to inversely obtain information from satellite-borne gravity observations on salinity variations.

Automated summary

The Gravity Recovery and Climate Experiment (GRACE) and its successor, the GRACE Follow-On (GRACE-FO) gravity satellite missions, have been providing monthly gravity field solutions for almost 20 years, enabling a unique opportunity to monitor large-scale mass variation processes. The method of determining the gravity anomaly time series from GRACE and GRACE-FO monthly solutions has been improved by considering the mass variations of the Caspian Sea. The gravity anomaly time series was then compared to water mass changes determined by considering variations in the salinity and temperature of seawater.