Gravity variations determined from GRACE and GRACE-FO monthly solutions for analyzing water mass changes in the Aral Sea

Abstract

The GRACE large-scale sequent GRACE-FO gravity satellite mission is 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 derived for the period of April 2002 to January 2022. The method of determining gravity anomaly time series from GRACE and GRACE-FO monthly solutions has been improved by taking into account the mass variations of the Caspian Sea. The gravity anomaly time series then has been compared to mass anomaly estimates. For deriving mass anomaly, beyond the available water volume data, density variations were determined by taking into account salinity and temperature changes. Unfortunately, no reliable information either on the salinity or on water temperature changes is available or accessible. Furthermore, not only the data but also the methodology of determining the density is not reliable. Still, the tests suggest that slight improvement in correlation due to the involvement of salinity information occurs.