As one of the world's leading glaciologists, Professor Jemma Wadham has devoted her career to the glaciers that cover one-tenth of the Earth's land surface. Today, however, these 'ice rivers' are in peril. High up in the Alps, Andes and Himalaya, once-indomitable glaciers are retreating; in Antarctica, meanwhile, thinning ice sheets are releasing meltwater to sensitive marine foodwebs, and may be unlocking vast quantities of methane stored deep beneath them. The potential consequences for humanity are almost unfathomable.