Everyone in the Arctic lives on the ice, even in summer. But, in summer, the ice is just below the soil, and if it melts, a whole town might sink into the sand. Silent Sound visited Herschel Island, where scientists are studying permafrost. Permafrost is very soft ground that is saturated with water and remains frozen throughout the year. This creates a very solid foundation - if it remains frozen. But the island is slowly sinking because its permafrost is melting due to climate change. Chris Burn, of the department of geology at Carlton University and one of Canada's permafrost experts, was visiting the island, as he has done for decades. 'We know there has been a 2-degree [Celsius] warming of the permafrost in the past century. It's harder to know how much of that has occurred in the past 50 years,' he said. 'This is happening because of higher air temperatures on the surface.' At 15 metres below the surface, the permafrost is now minus 8 degrees Celsius. The deeper it is, the colder it gets. Melting permafrost is a big problem in the Arctic because many communities have to rebuild roads and buildings that are falling down because the ground is shifting as it warms. Construction costs are high because the roads are bad and most of the materials are brought in by airplane. Herschel Island, which was a key harbour for whaling ships 100 years ago, used to be the home of the Mackenzie family. They moved away about 20 years ago, but they come back for a vacation every year. Marjorie Mackenzie was born in the old family log cabin which is now surrounded by a growing puddle of water. 'It's just getting a lot warmer. There's more water right here by the house. This bit of water right in front was never there,' she said.