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Antarctic Ice Sheet's erratic behaviour

A team from the University of Leeds and Aberystwyth University has returned from the Antarctic Peninsula with exciting new information on the behaviour of the giant Antarctic Ice Sheet.

The Antarctic Ice Sheet is of exceptional interest to geoscientists due to its size and location, which mean that it reacts quickly and dynamically to climate change. The team of four found that the ice sheet had expanded and then retreated across neighbouring James Ross Island several times over the last 25,000 years. The findings are crucial for understanding the thickness and extent of the ice sheet through time, and so its past and future contribution to sea level rise.

 

The group spent seven weeks in a field camp on the Ulu Peninsula - which forms part of James Ross Island - mapping in detail an area of 600 km2. They examined the distribution of so-called 'erratic' rocks on the Peninsula, a term used to refer to stones and boulders that have been moved from their original site by glaciers and ice sheets. The team found hundreds of large granite boulders scattered all across the Peninsula despite the islands' volcanic make-up, indicating that they were ripped up by the Antarctic Ice Sheet and moved to their new location.

 

"Geologically, the Antarctic Peninsula is completely different to James Ross Island - so we know that wherever we find these erratic rocks we can be fairly sure that an ice sheet from the Antarctic Peninsula brought them onto the island" said Dr Jonathan Carrivick, from the University of Leeds. "It is then a relatively easy task to match the exact composition of the rocks to those on the Antarctic Peninsula. In doing so, we can trace the historic movement of the ice sheet across the Prince Gustav Channel".

 

Principal Investigator Professor Neil Glasser, from Aberystwyth University, added: "The granite 'erratics' were ripped up by the Antarctic Ice Sheet and moved onto James Ross Island at some time in the past when the Ice Sheet was much more extensive and thicker. We were surprised both by the number and the size of these erratic boulders. Some are up to 3 metres in diameter - the size of a small family car".

 

The burning question is when the Antarctic Ice Sheet was big enough to have brought all these granite erratic boulders onto James Ross Island.

 

To try and answer this, the team collected rock samples from the surface of more than 50 granite boulders. These samples will be used to date precisely the former expansion of the Antarctic Ice Sheet, using a laboratory technique called cosmogenic exposure age dating.

 

"This dating technique works because we can use the build-up of cosmogenic isotopes in the granite rocks to gain an understanding of the length of time for which the boulders have been exposed on the surface of the Earth," said Dr Bethan Davies, from Aberystwyth University. "It is a relatively new technique but it will help us answer the important question of when the Antarctic Ice Sheet was bigger in the past. We will then be in a position to understand better the possible future behaviour of the ice sheet and its likely effect on rises in sea level".

 

The research was funded by the UK Natural Environment Research Council and supported by the British Antarctic Survey (BAS), who organised the fieldwork on James Ross Island. BAS supplied all the fieldwork logistics including transport, the field camp and safety equipment. The team of three scientists were also accompanied by a Field General Assistant from BAS.

 

For more information:

 

Images and interviews are available upon request.

 

Please contact:

 

Steve Akehurst, University of Leeds press office, 0113 343 4196, S.R.Akehurst@leeds.ac.uk

 

Arthur Dafis, Communications and Public Affairs, Aberystwyth University, 01970 621763/07841 979 452, aid@aber.ac.uk

Notes to editors

The 2008 Research Assessment Exercise showed the University of Leeds to be the UK's eighth biggest research powerhouse. The university is one of the largest higher education institutions in the UK and a member of the Russell Group of research-intensive universities. The university's vision is to secure a place among the world's top 50 by 2015. http://www.leeds.ac.uk

 

Established in 1872, Aberystwyth (www.aber.ac.uk) is a leading teaching and research university and was awarded a Queen's Anniversary Prize for Higher and Further Education in 2009. In 2010 the National Student Survey placed Aberystwyth in the top five institutions in the UK for student satisfaction. It is a leading centre for the study of climate change and has recently embarked on a £25m investment programme in new teaching and research facilities. Since its foundation in 1994, the Centre for Glaciology has become one of the leading British research groups concerned with the study of glaciers and their sedimentary products. http://www.aber.ac.uk/en/iges/research-groups/centre-glaciology/

 

British Antarctic Survey (BAS), a component of the Natural Environment Research Council, delivers world-leading interdisciplinary research in the Polar Regions. Its skilled science and support staff based in Cambridge, Antarctica and the Arctic, work together to deliver research that underpins a productive economy and contributes to a sustainable world. Its numerous national and international collaborations, leadership role in Antarctic affairs and excellent infrastructure help ensure that the UK maintains a world leading position. BAS has over 450 staff and operates five research stations, two Royal Research Ships and five aircraft in and around Antarctica.

 

The Natural Environment Research Council (NERC) is the UK's main agency for funding and managing world-class research, training and knowledge exchange in the environmental sciences. It coordinates some of the world's most exciting research projects, tackling major issues such as climate change, environmental influences on human health, the genetic make-up of life on earth, and much more.   NERC receives around £400 million a year from the government's science budget, which it uses to fund independent research and training in universities and its own research centres. www.nerc.ac.uk