Sudden climate shifts in the past may help pinpoint global warming impacts
By Summit Voice
SUMMIT COUNTY — The human-caused global warming of our era is measured on a scale of decades and centuries at best, but the Earth has cycled through much longer-term changes.
Climate records compiled this by a joint Japanese-American Integrated Ocean Drilling Program show that about 53 million years ago, the climate in Antarctica was characterized by warm, sub-tropical conditions during a time when carbon dioxide levels in the atmosphere were ten times greater than today.
New core samples collected during a research expedition this year are unique because they provide the world’s first direct record of waxing and waning of ice in this region of Antarctica.
But then, in a span of only 400,000 years, carbon dioxide levels dropped dramatically. Global temperatures dropped and Antarctica became ice-bound as glaciers quickly grew into ice sheets.
Watch this video from the expedition
Since the Arctic and Antarctic regions exert a huge influence over the global climate, it’s crucial to understand the regions in order to made accurate predictions about how global warming might play out.
Giant ice sheets in Antarctica reflect solar energy and moderate the world’s temperatures. Changes in the ice sheets contribute to the rise and fall in sea level and affect ocean circulation, which, in turn, regulates climate by transporting heat around the planet.
Now, scientists are trying to learn how and why the Earth’s climate has shifted so abruptly in the past, and how stable the polar ice sheets may be in the future. Earlier this year, the Integrated Ocean Drilling Program sent an international team of scientists to Antarctica as part of the Wilkes Land Glacial History Expedition.
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. The researchers took geological samples from the seafloor near the coast of Antarctica, recovering about 2,000 meters of sediment cores.
“These sediments are essential to our research because they preserve the history of the Antarctic ice sheet,” said Dr. Carlota Escutia of the Research Council of Spain CSIC-University of Granada, who led the expedition, along with co-chief scientist Dr. Henk Brinkhuis of Utrecht University in the Netherlands.
“We can read these sediments like a history book,” Brinkhuis explained. “And this book goes back 53 million years, giving us an unprecedented record of how ice sheets form and interact with changes in the climate and the ocean.”
The 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.
Understanding the behavior of Antarctica’s ice sheets will help build reliable global climate models to predict future climate.The science team now embarks on a multi-year process of on-shore analyses to further investigate the Wilkes Land cores.
Age-dating and chemistry studies among other analyses are expected to resolve changes in Antarctica’s climate over unprecedented short timescales (50-20,000 years). Data collected from the Wilkes Land expedition will complement previous research from drilling operations conducted elsewhere in the Antarctic over the last 40 years. Together, this research will provide important age constraints for models of Antarctic ice sheet development and evolution, thereby forming the basis for models of future ice sheet behavior and polar climatic change.