Washington, Feb 29 : Scientists have found new evidence of climate change that may help 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, a team of scientists from Cardiff University's School of Earth and Ocean Sciences, led by Dr Carrie Lear, Lecturer in Palaeoceanography, has presented new temperature records using ancient sea floor mud recovered from Tanzania, East Africa.
The shell chemistry of pin-head sized animals called foraminifera reveal that ocean temperatures did in fact cool by about 2.50C.
According to Dr Lear, "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," he added.
"Forams are great tools for studying climates of the past, which helps us learn about the uncertainties of our future greenhouse climate," said Dr Lear.
"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," he added.
The team at Cardiff University will now look for evidence of the ultimate cause of the global cooling using the forams.
According to them, 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.