Despite present-day conditions, Antarctica was not always covered with ice. Approximately 53 million years ago, the continent was a warm, sub-tropical environment and atmospheric CO2 levels exceeded today's by ten times.

But in just 400,000 years – a mere blink of an eye in geologic time –  Antarctica's lush environment transitioned into its modern icy realm. Concentrations of atmospheric carbon dioxide decreased, global temperatures dropped, ice sheets developed and Antarctica became ice-bound.

How did this change happen so abruptly and how stable can we expect ice sheets to be in the future? New ice core data retrieved from the Wilkes Land region of Antarctica may help answer those questions.

Wilkes Land is the region of Antarctica that lies due south of Australia, and is believed to be one of the more climate-sensitive regions of the polar continent.
(photo credit: wikipedia)

The new cores tell the story of Antarctica's transition from an ice-free, warm, greenhouse world to an ice-covered, cold, dry "icehouse" world. Sediments and microfossils preserved within the cores document the onset of cooling and the development of the first Antarctic glaciers and the growth and recession of Antarctica's ice sheets. Cores from one site resemble tree rings – unprecedented alternating bands of light and dark sediment preserve seasonal variability of the last deglaciation that began some 10,000 years ago.

The new core samples were collected during the Integrated Ocean Drilling Program's "Wilkes Land Glacial History" Expedition. They provide the world's first direct record of waxing and waning of ice in this region of Antarctica.

Understanding the behavior of Antarctica's ice sheets plays a fundamental role in the development of robust, effective global climate models. "These models rely on constraints imposed by data from the field," the researchers explained. "Measurements of parameters such as age, temperature, and carbon dioxide concentration provide invaluable inputs that help increase the accuracy of these models. The more we can constrain the models, the better they'll perform – and the better we can predict ice sheet behavior."