miércoles, 8 de agosto de 2012

RV: Antarctica's tropical past

Fuente: University of Southampton News
Expuesto el: jueves, 02 de agosto de 2012 4:00
Autor: University of Southampton News
Asunto: Antarctica's tropical past


Antarctica's tropical past

Ref: 12/133

02 August 2012

A a 52 million year-old pollen grain from Antarctica

Image credit: Lineth Contreras, Goethe University Frankfurt.

A new study has found that tropical vegetation, including palms and relatives of today’s tropical Baobab trees, once grew on the coast of Antarctica.

An international research team, led by scientists at Goethe University and the Biodiversity and Climate Research Centre in Frankfurt, Germany and involving the University of Southampton, has discovered that an intense warming event occurred in Antarctica 52 million years ago.

The study, published in the journal Nature, highlights the extreme contrast between modern and past climatic conditions on Antarctica and the extent of global warmth during periods of elevated atmospheric carbon dioxide (CO2) levels.

The scientists were able to identify and reconstruct characteristics of Antarctic vegetation by analysing rock samples from marine drill cores, which were obtained off the coast of Wilkes Land, Antarctica, as part of the Integrated Ocean Drilling Program (IODP). The rock samples are between 53 and 46 million years old and contain fossil pollen and spores that are known to originate from the Antarctic coastal region.

Dr Steve Bohaty, Postdoctoral Researcher in Ocean and Earth Science at the University of Southampton, who is based at the National Oceanography Centre, Southampton was co-author of the study. He explains: “This study provides new insight into climatic conditions in Antarctica during greenhouse episodes in the distant geological past. Our temperature and vegetation reconstructions show that Antarctica was once much warmer than today, with nearly tropical conditions in the high southern latitudes during peak warmth 52 million years ago.”

Around 52 million years ago, the concentration of the greenhouse gas CO2 in the atmosphere was more than twice as high as today. If current CO2 emissions continue unabated due to the burning of fossil fuels, CO2 concentrations in the atmosphere, as they existed 10s of millions of years ago, are likely to be achieved within a few hundred years.

Climate scientists are therefore particularly interested in warm periods in the geological record as they can be used to better understand mechanisms and processes in the climate system. Computer models indicate that future climate warming will be particularly pronounced in the polar regions. Until now, however, it has been unclear how Antarctic terrestrial ecosystems responded in the geological past to a greenhouse climate with high atmospheric CO2 concentrations.

The new study also demonstrates that the winter temperatures on the Wilkes Land coast of Antarctica were warmer than 10 degrees Celsius at that time, which is in sharp contrast to modern winter temperatures of approximately -20 degrees Celsius. The extremely elevated temperatures documented in Antarctica further imply that temperature differences between equatorial and polar regions were significantly smaller than previously thought.

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