Monday, September 14, 2009

Antarctica, Greenland helps scientists to understand past climate


Ice cores from Antarctica, Greenland and elsewhere in the world serve as a way for scientists to travel back in time to understand past climate. They analyze such things as the trapped bubbles of gas, chemicals, insoluble dust and trace metals found in the ice to reconstruct the cycles of glacial advance and retreat, the waxing and waning of temperature, the sudden appearance of droughts and volcanic eruptions.

But those long, skinny cylinders of ice can only tell so much of the story, according to Ryan Bay, a research physicist at the University of California Berkley. Bay and colleagues use an instrument they developed called an optical dust logger to measure the dust and particulates, or bits of matter, not captured by the original ice core.

Bay and team member Delia Tosi will take the latest and greatest version of their optical dust logger to Antarctica this coming field season. They’ll send the instrument down the deepest hole ever drilled in the ice sheet, where European scientists recovered the oldest ice to date from a high-altitude spot on the polar plateau called Dome C in East Antarctica.

The 3,270-meter-long ice core drilled by the European Project for Ice Coring in Antarctica (EPICA) reaches back at least 800,000 years. Bay said he is particularly interested in the last 100,000 years of climate history and finding signatures of volcanic eruptions and impacts from comets or asteroids that may have caused abrupt climate changes.

For instance, a major volcanic eruption can send a great amount of sulfate particles into the atmosphere. The sulfate aerosols reflect sunlight, effectively shielding the lower atmosphere of the planet and cooling it near the surface. Bay said this abrupt cooling event could then affect the succeeding climate for millennia.