Most glaciers in Greenland and Antarctica flow into the sea, and some of them terminate in extensive ice shelves – flat expanses of glacier ice, which can be the size of France, floating in the sea. Such ice shelves act as a buttress for their glaciers, slowing their flow.

In the polar regions, warming air temperatures may have little impact on surface melting if it is still well below freezing, but a slight warming in the ocean can have a huge impact on floating glacier tongues and ice shelves. As the floating ice thins, warm ocean water can gain access to growing portions of glaciers’ undersides, pushing the line where the ice loses contact with the seabed landwards. The result is yet more melt – a vicious cycle can ensue.

But Olivier Gagliardini and his colleagues find that things are not quite so simple. Using the most accurate numerical model yet, they show that the main impact of ice-shelf melt occurs inland, on grounded ice. The mass of an ice shelf determines how effectively it can hold back the glaciers which feed it, so their buttressing effect becomes weaker as more ice melts. The precise impact of ice melt in the sea is very subtle and highly dependent on where exactly the floating ice melts. While this paper does not provide a straightforward answer, it does demonstrate the importance of key studies using the most precise models, even if they require supercomputers to run them.

Ice2sea Work Package:  WP2.1

Publication:

Gagliardini, O., G. Durand, T. Zwinger, R. Hindmarsh, and E. Le Meur (2010), Coupling of ice-shelf melting and buttressing is a key process in ice-sheets dynamics, Geophysical Research Letters, 37, 14501-14506.