SOCORRO, N.M., October 17, 2001 -- An international research team, including a researcher from New Mexico Tech, has found evidence in deep-sea sediment cores taken from Antarctica's Ross Sea that the Earth's natural "wobble" may have directly influenced fluctuating global temperatures, as well as variations in ice volumes on the frozen continent, during a period between 34 and 15 million years ago.
A research paper detailing the study, titled "Orbitally induced oscillations in the East Antarctic ice sheet at the Oligocene/Miocene boundary," has been published in the current issue of the prestigious science journal Nature.
New Mexico Tech geochronologist William C. McIntosh played a major role in the study by accurately dating volcanic ash layers in the core samples, using an argon dating method employed at the New Mexico Tech Geochronology Research Laboratory.
McIntosh also serves as a volcanologist with the New Mexico Bureau of Geology and Mineral Resources and as an assistant professor of geochemistry at New Mexico Tech.
In the Nature paper, the geoscientists present sediment data from shallow marine cores drilled over the past 30 years in the western Ross Sea that link the varying thickness of the East Antarctic ice sheet directly to the Earth's orbital cycles, particularly the frequencies of wobble present in the planet's rotation and orbit over the course of tens to hundreds of thousands of years.
"The Antarctic ice sheet records show that ice sheet behavior has been much more responsive to this 'heartbeat' of the Earth's orbit than had been previously thought," McIntosh said.
Between 34 and 15 million years ago, when planetary temperatures were nearly 10 degrees (Fahrenheit) warmer than present averages and atmospheric carbon dioxide concentrations were twice as high as today, the Antarctic ice sheets were less stable than at present, the researchers wrote in their paper.
These findings may have modern-day implications with respect to changes in climate, particularly in regard to mounting concerns about global warming and escalating levels of carbon
dioxide and other "greenhouse" gases in the Earth's atmosphere.
In other studies, scientists have estimated that the amount of freshwater that can be melted out of the Antarctic ice sheets is enough to elevate the Earth's sea level by 200 feet -- a scenario which has played out repeatedly over the eons.
"There have been tremendous variations in the Earth's climate from Ice Age to Ice Age," McIntosh related. "For example, you can go to places in Texas where you can see that sea level was about 21 feet higher just 120 thousand years ago.
"We're currently in an interglacial period," he added, "and, as far as the future is concerned, nobody knows for sure what's going to happen with climate. . . . Although it is likely that
over the next million years, Earth will go in and out of Ice Ages as it has for the last two million years."