Video Transcript: Runaway Glaciers in West Antarctica

We are heading towards a particular sector of West Antarctica draining into the Amundsen Sea. This sector is drained by six glaciers. The biggest ones are Pine Island glacier and Thwaites glacier.

The speed of the glaciers measured by satellite is shown in color code; red is fast, blue is slower and green is the slowest.

The glaciers flow into the sea and form floating extensions called, "ice shelves."

Now, in red, are the areas where the flow speed is increasing almost every year. The darker the red, the more the glacier has been speeding up. You see that all the glaciers are speeding up.

Now, we focus our attention on the Smith glacier, which is a smaller glacier, but which has experienced some of the most dramatic changes.

The grounding line of Smith glacier in 1996 is at the transition boundary between the blue color, the ice shelf, and the white color, ice resting on the continent.

Now, we transition to 2011. The grounding line is 35 kilometers farther back, a retreat of nearly two kilometers per year.

If we could peal off the ice from the continent and see the bed, this is what it would look like. The arrows indicate the flow direction of ice. The color indicates the speed; blue is slow, red is fast.

We see that the glaciers flow on top of major subglacial valleys, colored in brown; t he darker the brown and color, the deeper the valleys.

As the glaciers retreat, they will follow these deep valleys. There is no mountain or big hill along the way that could act as a barrier to hold these glaciers back.

The glaciers speed up, the grounding lines retreat, the deep valleys that are sloping inland, all reinforce each other to make the retreat of ice in this part of Antarctica unstoppable. And we think that this is what is happening right now.