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Persistent near-tropical warmth on the Antarctic continent during the early Eocene epoch
Pross, J철rg,Contreras, Lineth,Bijl, Peter K.,Greenwood, David R.,Bohaty, Steven M.,Schouten, Stefan,Bendle, James A.,R철hl, Ursula,Tauxe, Lisa,Raine, J. Ian,Huck, Claire E.,van de Flierdt, Tina,Jamieso Nature Publishing Group, a division of Macmillan P 2012 Nature Vol.488 No.7409
The warmest global climates of the past 65 million years occurred during the early Eocene epoch (about 55 to 48 million years ago), when the Equator-to-pole temperature gradients were much smaller than today and atmospheric carbon dioxide levels were in excess of one thousand parts per million by volume. Recently the early Eocene has received considerable interest because it may provide insight into the response of Earth??s climate and biosphere to the high atmospheric carbon dioxide levels that are expected in the near future as a consequence of unabated anthropogenic carbon emissions. Climatic conditions of the early Eocene ??greenhouse world??, however, are poorly constrained in critical regions, particularly Antarctica. Here we present a well-dated record of early Eocene climate on Antarctica from an ocean sediment core recovered off the Wilkes Land coast of East Antarctica. The information from biotic climate proxies (pollen and spores) and independent organic geochemical climate proxies (indices based on branched tetraether lipids) yields quantitative, seasonal temperature reconstructions for the early Eocene greenhouse world on Antarctica. We show that the climate in lowland settings along the Wilkes Land coast (at a palaeolatitude of about 70째 south) supported the growth of highly diverse, near-tropical forests characterized by mesothermal to megathermal floral elements including palms and Bombacoideae. Notably, winters were extremely mild (warmer than 10??째C) and essentially frost-free despite polar darkness, which provides a critical new constraint for the validation of climate models and for understanding the response of high-latitude terrestrial ecosystems to increased carbon dioxide forcing.
Reorganization of Southern Ocean Plankton Ecosystem at the Onset of Antarctic Glaciation
Houben, Alexander J. P.,Bijl, Peter K.,Pross, Jö,rg,Bohaty, Steven M.,Passchier, Sandra,Stickley, Catherine E.,Rö,hl, Ursula,Sugisaki, Saiko,Tauxe, Lisa,van de Flierdt, Tina,Olney, Matthew,San American Association for the Advancement of Scienc 2013 Science Vol.340 No.6130
<P><B>Southern Change</B></P><P>Antarctica has been mostly covered by ice since the inception of large-scale continental glaciation during the Oligocene, which profoundly altered the isotopic and mineralogical records of the sediments surrounding the continent. <B>Houben <I>et al.</I></B> (p. 341) found records of the corresponding living systems in the fossil marine dinoflagellate cysts, which revealed that a microplankton ecosystem, similar to the one that exists today, appeared simultaneously with the first major Antarctic glaciation approximately 34 million years ago.</P>