News

Research student sheds new light on melting ice sheets

(5 August 2005)

A Durham University research student has captured the attention of the world’s earth scientists by uncovering new ideas about the melting of polar ice sheets and sea-level change.

Sophie Bassett, who is completing her PhD studies with Dr Glenn Milne in the Department of Earth Sciences at Durham, has had her work selected for publication in the prestigious international journal Science.

Her research, carried out in collaboration with scientists at the University of Toronto, Canada and Oregon State University (Corvallis), USA, provides important evidence that will help to explain the processes that brought the Earth out of the last ice age.

Dr Milne said: “This work resolves a long outstanding issue with regard to understanding observations of sea-level change in equatorial regions during the most recent global deglaciation. It supports the idea that the Antarctic ice sheet melted earlier than commonly thought causing a chain of events that accelerated the melting of the massive northern hemisphere ice sheets.”

Bassett and her colleagues used a sophisticated computer model of ice age sea-level change. Their report, published in Science on 5 August, shows that the sea-level data can be used to provide important information that relates to ice age climate change and properties of material within the deep Earth. Specifically, the sea-level observations can be explained only if two key criteria are satisfied.

The first of these criteria is that the Antarctic ice sheet melted earlier and more rapidly than is currently thought. This challenges the more conventional idea that the Antarctic ice sheet began melting relatively late in response to sea-level rise driven by ice melting in the northern hemisphere. The findings of Bassett and her colleagues add to a small number of recent studies that suggest the reverse scenario: the Antarctic ice sheet melted relatively early and thus acted as a causal mechanism for accelerated melting of northern hemisphere ice sheets through complex interactions within the climate system.

The second criterion required to explain the sea-level observations is that material deep within the solid Earth (about 670-2900km) is mechanically stronger than material above this region by almost two orders of magnitude. It relates to the strength (or viscosity) of the Earth’s mantle with depth, and has important implications for understanding of the geological evolution of the solid Earth.

Dr Milne explained: “The viscosity structure of the Earth’s mantle is known to be one of the main controls on the large-scale geometry of material flow within this region and, as a consequence, the motion of the surface tectonic plates over geological timescales.”

Sophie Bassett, who comes from Newcastle, took her BSc in Geophysics at Edinburgh and is currently writing up her PhD thesis. She has secured funding to pursue her research interests as a Marie-Curie postdoctoral fellow at the Alfred Wegener Institute for Polar Research in Bremerhaven, Germany.

Ms Bassett said: “This has been a fascinating project to be involved in and I’m delighted that my work has been so well received. I look forward to pursuing this research further through my postdoctoral fellowship.

Contacts: Dr Glenn Milne, Lecturer in Geophysics 0191 334 2332g.a.milne@durham.ac.uk Sophie Bassett 07740461239s.e.bassett@durham.ac.uk