Legacy of the Ice Age: How does the Earth’s crust deform when ice sheets melt?

Our planet’s crust consists of a variety of rock types which, given high enough pressure, can undergo gradual deformation. Since matter is not evenly distributed on the Earth and some areas, such as the ice sheets of Greenland and Antarctica, support a greater weight than others, this means that the planet is not quite spherical.

At the end of the last ice age some 10,000 years ago, billions of tons of ice covering parts of North America and Europe melted. This caused a major redistribution of mass on the Earth, but the crust responds to such changes so slowly that it is still deforming in response to these events. This process is known as Glacial Isostatic Adjustment, or GIA, and affects regional sea levels, which are controlled to an extent by the exact shape of the Earth.

In this paper, Giorgio Spada and his colleagues examine the effect of predicted mass changes of glaciers and ice sheets on sea levels around the world. They use a new, very flexible set of assumptions about the properties of the Earth’s crust, allowing them to model GIA more realistically. This is important in order to understand how sea levels will develop in different parts of the world – in response not just to the melting of glaciers and ice caps, but also to the resulting change in the shape of the Earth.

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Spada, G., F. Colleoni, and G. Ruggieri (2011), Shallow upper mantle rheology and secular ice-sheets fluctuations, Tectonophysics, 511(3-4), 89-98.


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