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Snapshot of past climate reveals no ice in Antarctica millions of years ago

28 July 2008

A snapshot of New Zealand's climate 40 million years ago reveals a greenhouse Earth, with warmer seas and little or no ice in Antarctica, according to research published this week in the journal Geology.

The study suggests that Antarctica at that time was yet to develop extensive ice sheets. Back then, New Zealand was about 1100 km further south, at the same latitude as the southern tip of South America - so was closer to Antarctica - but the researchers found that the water temperature was 23-25°C at the sea surface and 11-13°C at the bottom.

"This is too warm to be the Antarctic water we know today," said Catherine (Cat) Burgess from Cardiff University and lead-author of the paper. "And the seawater chemistry shows there was little or no ice on the planet."

These new insights come from the chemical analysis of exceptionally well preserved fossils of marine micro-organisms called foraminifers, discovered in marine rocks from New Zealand. The researchers tested the calcium carbonate shells from these fossils, which were found in 40 million-year-old sediments on a cliff face at Hampden Beach, South Island.

"Because the fossils are so well preserved, they provide more accurate temperature records" said Cat. "Our findings demonstrate that the water temperature these creatures lived in was much warmer than previous records have shown."

"Although we did not measure carbon dioxide, several studies suggest that greenhouse gases forty million years ago were similar to those levels that are forecast for the end of this century and beyond.

Our work provides another piece of evidence that, in a time period with relatively high carbon dioxide levels, temperatures were higher and ice sheets were much smaller and likely to have been completely absent."

The rock sequence from the cliff face covers a time span of 70,000 years and shows cyclical temperature variations with a period of about 18,000 years. The temperature oscillation is likely to be related to the Earth's orbital patterns.

The research was funded by the Natural Environment Research Council, the Netherlands Organisation for Scientific Research (NWO) and GNS Science, New Zealand.

Further information

Cat Burgess
School of Earth and Ocean Sciences
Cardiff University
Mob: 07740 500 722

Lowri Jones, Press Office
Cardiff University
Tel: 029 20 870 995

NERC Press Office
Natural Environment Research Council
Polaris House, North Star Avenue
Swindon, SN2 1EU
Tel: 01793 411561
Mob: 07917 557215

Notes

1. 'Middle Eocene climate cyclicity in the Southern Pacific: Implications for global ice volume' is published in the August issue of Geology. (vol.36, no.8, p.651-654; doi:10.1130/G24762A.1)
The authors are:
Catherine E. Burgess, Cardiff University (lead author)
Paul N. Pearson and Caroline H. Lear, Cardiff University
Hugh E.G. Morgans, GNS Science New Zealand
Luke Handley and Richard D. Pancost, University of Bristol
Stefan Schouten, Royal Netherlands Institute for Sea Research

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.

3. The Natural Environment Research Council (NERC) funds world-class science, in universities and its own research centres, that increases knowledge and understanding of the natural world. It is tackling major environmental issues such as climate change, biodiversity and natural hazards. NERC receives around £400m a year from the government's science budget, which is used to provide independent research and training in the environmental sciences.

Press release: 38/08