Abstract:
Sri Lanka has been recognised as one of the places with the lowest gravitational measurement
on Earth. However, the factors contributing to this phenomenon remain largely unexplored.
The study examined the impact of Groundwater Storage (GWS) and fluctuations in sea level on
regional gravitational anomalies by utilising satellite-based remote sensing data. An analysis of
Gravity Recovery and Climate Experiment (GRACE) and Gravity Recovery and Climate Experiment
Follow-On (GRACE-FO) models, along with gravity data from the International Centre
for Global Earth Models (ICGEM), CG-6 terrestrial gravity readings, Bureau Gravimétrique International
(BGI) terrestrial and marine gravity data, and Global Land Data Assimilation System
(GLDAS) hydrological information was conducted to discern how the redistribution of mass resulting
from hydrological and oceanographic activities influences gravity across terrestrial and
oceanic regions. The investigation spanned the timeframe from 2018 to 2022 and employed
methodologies including kriging interpolation, Pearson correlation, and time series regression
to identify spatial and temporal trends. The results unveiled important statistical connections
among gravity anomalies and sea level indicators. The correlation coefficient of gravity to sea
surface height (SSH) was R² = 0.6183, and it registered R² = 0.6029 against sea level anomaly
(SLA), which suggests that more than 60% of gravity variations could be attributed to ocean
mass redistribution. This connection of gravity to groundwater storage percentile (GWSP) was
even stronger and reached R² = 0.7577, validating that groundwater changes are an important
determining factor that acts upon gravity in the surveyed region. Long-term gravity observation
results from high as well as low gravity sites proved overall stability defined by small fluctuations
that could represent climatic action or small tectonic activity. This study revealed the
potential of satellite methods to monitor gravity variations resulting from mass changes in very
large and remote areas. It offered useful information about regional gravity anomalies of Sri
Lanka without recourse to expensive ground survey, and it enriched general knowledge about
geophysical and hydrologic processes.
