The Search For Earth's Underground Oceans - The water stored in the inner layers of Earth may be more plentiful — and important — than scientists previously thought

Title: 
The Search For Earth's Underground Oceans
 
Author:
Steve Nadis
 
Published:
Discovery Magazine, 11 June 2020
https://www.discovermagazine.com/planet-earth/the-search-for-earths-underground-oceans
 
From the article:
Early in Jacobsen’s career, his research adviser was Joseph Smyth, a geologist who had demonstrated that a mineral called wadsleyite could, in theory, hold significant amounts of water. Wadsleyite and its relative, ringwoodite, are the two main components of the transition zone between Earth’s upper and lower mantle — about 250 to 410 miles below the surface. When he embarked on his own research in the mid-1990s, Jacobsen wanted to know: How much water might actually be stored in these abundant minerals?