News Release 04-033
Glacial Records Depict Ice Age Climate in Synch Worldwide
March 24, 2004
This material is available primarily for archival purposes. Telephone numbers or other contact information may be out of date; please see current contact information at media contacts.
Arlington, VA—An answer to the long-standing riddle of whether the Earth's ice ages occurred simultaneously in the Southern and Northern hemispheres is emerging from glacial deposits found in the high desert east of the Andes.
The work, reported in the current (March/April) issue of the Geological Society of America Bulletin, is important because it reveals that ice ages were global in nature, a fact scientists had trouble determining due to the difficulty of precisely dating the jumble of debris—sand, gravel, clay and boulders—that ice-age glaciers leave in their wakes. The new work suggests ice ages occurred worldwide, in part, because of the sluggish redistribution of solar energy through the world's oceans punctuated by repeated, rapid cooling of the Earth's atmosphere.
"The results are significant because they indicate that the whole Earth experiences major ice-age cold periods at the same time, and thus, some climate-forcing mechanism must homogenize the Earth's climate system during ice ages and, by inference, other periods," says Michael Kaplan, a postdoctoral fellow at the University of Edinburgh who conducted the work at the University of Wisconsin (UW)-Madison.
Co-workers from the Woods Hole Oceanographic Institution also assisted in the study.
Using a technique to read the changes imposed by cosmic rays—charged, high-energy particles that bombard the Earth from outer space—on atoms found in the mineral quartz, the researchers were able to precisely date a sequence of moraines, ridge-like glacial features composed of an amalgam of rocks, clay, sand and gravel. Their results show that glacial ice in South America reached its apex 22,000 years ago and had begun to disappear by 16,000 years ago.
"The team has applied an innovative investigative technique to an untapped archive of data on natural climate variability to help reduce uncertainty in our knowledge of how Earth's climate works," said David Verardo, director of the National Science Foundation’s (NSF) paleoclimate program, which funded the research. NSF is the independent federal agency that supports fundamental research and education across all fields of science and engineering.
The work is certain to help researchers of past climates unravel the mysteries of ice ages that periodically gripped the planet, Verardo said, but it also will help those trying to understand current and future climate change by helping to determine the natural causes of changes in the Earth's climate system on a global scale.
"We've been able to get quite precise ages directly on these glacial deposits," says team leader Brad Singer, of UW-Madison. "We found that the structure of the last South-American ice age is indistinguishable from the last major glacier formation in the Northern Hemisphere."
And, said Kaplan, "During the last two times in Earth's history when glaciers formed in North America, the Andes also had major glacial periods."
The results address a major debate in the scientific community, according to Singer and Kaplan, because they seem to undermine a widely held idea that global redistribution of heat through the oceans is the primary mechanism that drove major climate shifts of the past.
The implications of the new work, say the study authors, support a different hypothesis: Rapid cooling of the Earth's atmosphere synchronized climate change around the globe during each of the last two glacial epochs.
"Because the Earth is oriented in space in such a way that the hemispheres are out of phase in the amount of solar radiation they receive, it is surprising to find that the climate in the Southern Hemisphere cooled off repeatedly during a period when it received its largest dose of solar radiation," says Singer. "Moreover, this rapid synchronization of atmospheric temperature between the polar hemispheres appears to have occurred during both of the last major ice ages that gripped the Earth."
The technique used by the team uses cosmic rays to determine how long material at the surface of the Earth has been exposed to the atmosphere. When the high-energy cosmic ray particles, which bombard the Earth from sources beyond the solar system, strike oxygen atoms in quartz on the surface of the Earth, they break apart, creating new atoms of an isotope known as 10-beryllium. The number of 10-beryllium atoms in a rock sample allows scientists to precisely date when a particular rock was deposited on the surface of the Earth by a glacier or some other mechanism.
According to the researchers, the dating method is relatively new, and requires reducing kilograms of quartz-bearing rock to about a million atoms of 10-beryllium in the laboratory. Those atoms are then analyzed using an accelerator mass spectrometer to determine how long ago the quartz was exposed to cosmic rays, which can only penetrate the top meter or so of the Earth.
-NSF-
Media Contacts
Cheryl Dybas, NSF, (703) 292-7734, email: cdybas@nsf.gov
Program Contacts
David Verardo, NSF, (703) 292-8527, email: dverardo@nsf.gov
The U.S. National Science Foundation propels the nation forward by advancing fundamental research in all fields of science and engineering. NSF supports research and people by providing facilities, instruments and funding to support their ingenuity and sustain the U.S. as a global leader in research and innovation. With a fiscal year 2023 budget of $9.5 billion, NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and institutions. Each year, NSF receives more than 40,000 competitive proposals and makes about 11,000 new awards. Those awards include support for cooperative research with industry, Arctic and Antarctic research and operations, and U.S. participation in international scientific efforts.
Connect with us online
NSF website: nsf.gov
NSF News: nsf.gov/news
For News Media: nsf.gov/news/newsroom
Statistics: nsf.gov/statistics/
Awards database: nsf.gov/awardsearch/
Follow us on social
Twitter: twitter.com/NSF
Facebook: facebook.com/US.NSF
Instagram: instagram.com/nsfgov