Peter Bijl on the Antarctic misunderstanding
On June 14th, Peter Bijl, paleo-oceanographer and a member of the Utrecht Young Academy since this year, conducted an interview with NRC on the origin and warming up of Antarctica.
There is a persistent misunderstanding about that, says Bijl. In the seventies, the ocean gateway hypothesis was developed: The ice cap would have come to existence due to Australia and South-America drifting away from Antarctica, creating a cold, rapid ocean current that circled eastward around Antarctica. As warm water stopped reaching Antarctica, it started cooling down. At the time this was a very good and substantial hypothesis.
Marine plankton
But this hypothesis is incorrect. By drilling and examining the sediment from the ground, Bijl and his exploration team are able to discover the water temperature from over millions of years ago. The team discovered that Antarctica has never been exposed to warm sea currents, due to the type of marine plankton found in the sediment. The idea that the drifting of Australia and South-America coincides with the emergence of the ice cap has also turned out wrong: There is a fifteen million-year gap between the two events.
Bijl provides the grand decrease of CO2 as alternative explanation: "The Antarctic was tropically hot 52 million years ago, with lots of rainfall, but after that the temperature decreased progressively. We know this because of the rate of boron isotopes in limestone, amongst other things." In his own research, Bijl focuses the sensitivity of the current ice cap for temperature rise by examining past changes in the ice cap.