How Do Glaciers Move?

Since the 18 fifties, most glaciers in the world have been retreating. And that's been accelerated dramatically in the past 30 or forty years. So what we have is a situation where the glacier, as i've said, at the lower altitudes, is a blating faster than its accumulating. The higher altitudes, its accumulating faster than its oblating. During the summer, the glacier as a whole, typically has positive oblation. It has a net mass loss during the summer and a net mass gain during the winter. Over all the course of the year, you might expect that to be roughly balanced if the glacier is sort of neither expanding nor retreating. But these days