| 1 | On the beach there is a jagged layer of thawing permafrost. | |
| 2 | An example of a tipping point is the thawing of the permafrost. | |
| 3 | There is 5, 000 miles of railway track built on permafrost. | |
| 4 | It is located in the ice-house - a cave hollowed out in the permafrost. | |
| 5 | The presence of sea ice and of permafrost helps protect Arctic barrier islands for much of the year. |