Antarctic Ice Cap 33.6 Million Years Old, Plankton Fossils Say

Scientists from Spain have found evidence the Antarctic icecap and modern ecosystem that surrounds it date back about 33.6 million years old, says a recent study published in the journal Science.

The time frame for the cap's formation was revealed through Antarctic core samples that contained the fossilized remnants of plankton --- which saw their populations shrink from a wide diversity of species to only a few hearty lines when glaciation set in at the south pole during the end of the Eocene Epoch and the beginning of the Oligocene Epoch, approximately 34 million years ago.

Before the climatic shift, Earth was a notably warmer planet where a generous assortment of plankton coursed through the waters in all stretches of the globe, according to the findings compiled by the Andalusian Institute of Earth Sciences, a joint effort between the Spanish National Research Council and University of Granada.

The new research focused on single-celled plankton called dinoflagellates, which, aside from containing materials that tend to become fossils, contain materials that fossilize, were extremely diverse before the Eocene-Oligocene transition. When the ice pack formed, however, only plankton that could survive cold temperatures and a seasonal cycle of melting, then freezing up again, remained.

Pre-glaciation sediment samples contained highly varied dinoflagellate communities, with star-shaped structures.

When the ice appeared 33.6 million years ago, dinoflagellate communities managed to survive, but ever since they've been undergoing constant change and evolution.

"The great change came when the [plankton] species simplified their form and found they were forced to adapt to the new climate conditions," said study researcher Carlota Escutia of the Andalusian Institute of Earth Sciences in Spain.

Different from Antarctica's long-standing ice cap, the ice pack is the floating sea ice that melts in the summer and freezes in the winter.

At melt time, plankton in the Southern Ocean surrounding the continent chow down on the nutrients freed up from the melting ice, setting in motion an even bigger feeding frenzy as plankton-eating species such as whales gorge themselves while they can.

"The explosion of dinoflagellates adapted to a temporary sea ice cover testifies to an in-depth reorganization of the food web in the Southern Ocean," study researcher Jörg Pross, a paleoclimatologist at Goethe University in Germany, said in a statement. "Our