And until recently, researchers thought that these water driven effects would be caused mainly by the melting of the glaciers and the ice caps. But when CEO and his collaborators tried to model the Earth's water content to account for how much the access has tilted, they couldn't find any fully explainable data, adding that the effects of changes in surface reservoirs did not help, says Co. Quote So I scratched my head and said, probably one effect is groundwater. End quote