The energy estimate done by the authors of the Annals of Glaciology paper, researchers at the Chicago and Princeton Universities, is based on "a simplified, but not completely unrealistic, rectangular geometry," according to Levermann. Using this model shape, they calculate the potential energy (due to the Earthีs gravity and water pressure) stored in the floating iceberg before and after roll over. The difference provides the energy released due to capsize, which can amount to the explosive energy of several thousands tons of TNT.