This interactive is focused on the "leading edge" of the polar glaciers, that first section of ice moving from land into the surrounding ocean.
In the channels of Greenland's long fjords, these leading edges form into glacial ice tongues. In Antarctica, the ice spills off the land in wider bays forming into apron-shaped ice shelves. In both poles, the mass of the leading ice edge acts as a dam holding back the flow of land ice behind it.
However, sitting in the water these areas are vulnerable to melting and weakening from a warming ocean and atmosphere. Large sections break apart, reducing the force holding back the land ice. Land ice pushes forward, accelerating the flow and moving more ice from the land into the ocean where this new addition of ice contributes to sea level rise.
The Interactive: The top cut in looks from above at a section of ice tongue like the one pictured above from Greenland. Swipe away sections of the leading ice edge to see the results on the tongue below. As it breaks apart ice pushes forward off the land into the ocean causing a loss of ice on land, the ice tongue to retreat and sea level to rise.