While these two examples are seasonal ......

While these two examples are seasonal and linked to the weather, in Alaska there are signs of climate-driven changes. "I think of Alaska as the 'canary in the cage' because it is very tectonically active, there are a lot of active faults, a lot of volcanoes and it's very high latitude and that is where the temperatures are rising most rapidly," says Bill McGuire, a volcanologist who heads the Benfield Hazard Centre at University College London.

In the south of Alaska, large glaciers sit over a major fault where the Pacific-Yukatat plate dips under the continent. During the past century, the glaciers that have pinned down and stabilised the fault have thinned by hundreds of metres, and the crust beneath has rebounded by up to 20 millimetres per year.

Ice loss was particularly fast during a warm spell between 2002 and 2006. The frequency of small earthquakes in the area increased during this time, according to Jeanne Sauber of NASA's Goddard Space Center in Maryland and Natalia Ruppert of the University of Alaska, Fairbanks. Sauber and Ruppert also think that the magnitude 7.2 St Elias earthquake in this region in 1979 occurred earlier than it might otherwise have done, due to the loss of ice (Geophysical Monograph Series, vol 179, p 369). The quake was in a unpopulated area and no one died.