The fraction of the water-loss rate when changing upper mantle melt fraction, ceteris paribus (left panel), and the evolution of the upper mantle melt fraction and amount of water in the mantle for a Type II evolution (right column). The vertical black dashed line in the left panel shows the time when the melt fraction drops below the estimated critical value of 0.05. Below a melt fraction of 0.05, the water-loss rate from the mantle begins to decrease with the melt fraction.