The Antarctic ice cap formed sometime around 33.6 million years ago, during the Oligocene epoch, according to new research from the Andalusian Institute of Earth Sciences (IACT) — a Spanish National Research Council-University of Granada joint center. The finding is supported by the data gained during a recent expedition to Antarctica by the IACT, where ice sediments from different depths were sampled.
Antarctica was a relatively warm place until the formation of the ice caps, and the Earth as a whole was much warmer. The research found that when the ice caps formed, that the high diversity of plankton found in the region was greatly reduced, leaving only the species suited to the new conditions, as a result of the glaciation.
Carlota Escutia, the IACT researcher who led the expedition, explains: “The fossil record of dinoflagellate cyst communities reflects the substantial reduction and specialization of these species that took place when the ice cap became established and, with it, marked seasonal ice-pack formation and melting began.”
Those plankton communities that remained at the time are essentially the beginnings of the plankton communities that are still there today, though they have of course changed some since then. Escutia says: “The great change came when the species simplified their form and found they were forced to adapt to the new climatic conditions.”
“Pre-glaciation sediment contained highly varied dinoflagellate communities, with star-shaped morphologies. When the ice appeared 33.6 million years ago, this diversity was limited and their activity subjected to the new seasonal climate.”
The researchers note that “when the ice-pack melts as the Antarctic summer approaches, this marks the increase in primary productivity of endemic plankton communities. When it melts, the ice frees the nutrients it has accumulated and these are used by the plankton.” Dr Escutia says: “this phenomenon influences the dynamics of global primary productivity.”
The new findings were recently published in the journal Science.