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Has The Mystery Of The Antarctic Ice Sheet Been Solved?

Date:
February 29, 2008
Source:
Cardiff University
Summary:
New evidence has been presented which could solve the puzzle of why Antarctica went into the deep freeze 34 million years ago -- and it comes from a surprising place. 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.

Foram called "Halkyardia minima", which is about the size of a pin-head.
Credit: Image courtesy of Cardiff University

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.

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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 2.5 degrees Celsius.

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.


Story Source:

The above story is based on materials provided by Cardiff University. Note: Materials may be edited for content and length.


Cite This Page:

Cardiff University. "Has The Mystery Of The Antarctic Ice Sheet Been Solved?." ScienceDaily. ScienceDaily, 29 February 2008. <www.sciencedaily.com/releases/2008/02/080228080541.htm>.
Cardiff University. (2008, February 29). Has The Mystery Of The Antarctic Ice Sheet Been Solved?. ScienceDaily. Retrieved February 27, 2015 from www.sciencedaily.com/releases/2008/02/080228080541.htm
Cardiff University. "Has The Mystery Of The Antarctic Ice Sheet Been Solved?." ScienceDaily. www.sciencedaily.com/releases/2008/02/080228080541.htm (accessed February 27, 2015).

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