A team of scientists from Cardiff University's School of Earth and Ocean Sciences and Amgueddfa Cymru - National Museum Wales travelled to Africa to find new evidence of climate change which helps explain some of the mystery surrounding the appearance of the Antarctic ice sheet.
Ice sheet formation in the Antarctic is one of the most important climatic shifts in Earth's history. However, previous temperature records show no evidence of the oceans cooling at this time, but instead suggest they actually warmed, presenting a confusing picture of the climate system which has long been a mystery in palaeoclimatology.
Now Dr Carrie Lear, Lecturer in Palaeoceanography, and her team at Cardiff have presented new temperature records using ancient sea floor mud recovered from Tanzania, East Africa. The shell chemistry of pin-head sized animals called foraminifera ("forams") reveal that ocean temperatures did in fact cool by about 2.50C.
Dr Lear said: "Forams are great tools for studying climates of the past, which helps us learn about the uncertainties of our future greenhouse climate. These new records help resolve a long-standing puzzle regarding the extent of ice-sheet growth versus global cooling, and bring climate proxy records into line with climate model simulations.
"We have been able to use the chemistry of the Tanzanian microfossils to construct records of temperature and ice volume over the interval of the big climate switch. These new records show that the world's oceans did cool during the growth of an ice sheet, and that the volume of ice would have fitted onto Antarctica; so now the computer models of climate and the past climate data match up."
The team at Cardiff University's School of Earth, Ocean and Planetary Sciences will now look for evidence of the ultimate cause of the global cooling using the forams. They believe the prime suspect is a gradual reduction of CO2 in the atmosphere, combined with a 'trigger' time when Earth's orbit around the sun made Antarctic summers cold enough for ice to remain frozen all year round.
The research is funded by NERC and published in the March issue of the Geological Society of America's journal Geology.
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Notes to Editors
1. Cardiff School of Earth and Ocean Sciences is one of the top geoscience units in the UK, rated 5A in most research independent Research Assessment Exercise. It is a large, international research school with more than 30 leading international research scientists, currently including two Fellows of the Royal Society. The postgraduate research school currently numbers about 35 students studying a diverse range of research problems. These researchers are addressing some of the most significant research themes in world science at the moment, including global change, the origin and evolution of life, environmental science, natural resource exploration, and the evolution of Earth and planets.
2. Cardiff University is recognised in independent government assessments as one of Britain's leading teaching and research universities. It is also ranked as one of the world's top 100 universities by the Times Higher Education Supplement (THES).
2008 marks the 125th anniversary of Cardiff University having been founded by Royal Charter in 1883. Today the University combines impressive modern facilities and a dynamic approach to teaching and research. The University's breadth of expertise in research and research-led teaching encompasses: the humanities; the natural, physical, health, life and social sciences; engineering and technology; preparation for a wide range of professions; and a longstanding commitment to lifelong learning.
Cardiff is a member of the Russell Group of the UK's leading research universities.
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