Upsala Glacier Retreat: Taken from the International Space Station, this photo highlights the snout of the Upsala Glacier on the Argentine side of the North Patagonian Icefield. Ice flow in this glacier comes from the north (right in this rotated image). Dark lines of rocky debris (moraine) within the ice give a sense of the slow ice flow from right to left. A smaller, side glacier joins Upsala at the present-day ice front -- the wall from which masses of ice periodically collapse into Lago (Lake) Argentino. In this image, the 2.7 kilometer-wide ice front casts a thin, dark shadow. The surface of Lago Argentino is whitened by a mass of debris from a recent collapse of the ice wall. Larger icebergs appear as white dots on the lake surface at image left. The water color in Lago Argentino is related to the glacier flow. The lake receives most of the ice from the glacier and thus receives most of the “rock flour” -- rocks ground to white powder by the ice scraping against the rock floor ...