[meteorite-list] Cosmic Dust in Ice Cores Sheds Light on Earth's Past Climate

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri Aug 4 12:56:03 2006
Message-ID: <200608041653.JAA09307_at_zagami.jpl.nasa.gov>

http://www.earthinstitute.columbia.edu/news/2006/story07-28-06b.php

Earth Institute News
July 28, 2006

Contact: Ken Kostel
212-854-9729 or kkostel_at_ei.columbia.edu

Contact: Clare Oh
212-854-5479 or coh_at_ei.columbia.edu

Cosmic Dust in Ice Cores Sheds Light on Earth's Past Climate

Each year nearly 40,000 tons of cosmic dust fall to Earth from outer
space. Now, the first successful chronological study of extraterrestrial
dust in Antarctic ice has shown that this amount has remained largely
constant over the past 30,000 years, a finding that could help refine
efforts to understand the timing and effects of changes in the Earth's
past climate.

The same study also used an improved analytical technique to show that
dust carried to Antarctica from continental sources changed depending on
climate.

The study, which appears in the July 28 issue of the journal Science,
involved researchers from the Lamont-Doherty Earth Observatory, a part
of The Earth Institute, and the Alfred Wegener Institute for Polar and
Marine Research (AWI) in Bremerhaven, Germany. The depth of the core
they examined corresponded to the period between 6,800 and 29,000 years
before the present day - a span that includes the height of the last
glacial period, and the transition to warm conditions similar to today.

The scientists collected particulate matter from the EPICA (European
Project for Ice Coring in Antarctica) ice core and measured the
concentration of helium-3 (3He), a rare isotope that is plentiful in the
sun's solar wind and is carried to Earth imbedded in cosmic dust
particles measuring just a few thousandths of a millimeter in diameter.
These dust particles carry their exotic helium load to the Earth's
surface where they are preserved in the snow and ice of the polar ice
caps, among other places.

Because ice cores from the polar caps provide a high-resolution temporal
record of the past, the researchers were able to measure fine variations
in the rate of cosmic dust accumulation between glacial and interglacial
periods as well as the helium isotope characteristics of these rare
particles. They found that the accumulation of cosmic dust did not
change appreciably as the Earth emerged from the last great Ice Age and
entered the current warm period, a fact that is likely to bolster the
use of cosmic dust measuring techniques in future climate studies.

In addition, this was the first study to examine both cosmic and
terrestrial dust using the same helium-isotope technique. As a result,
they also found that the composition of mineral dust particles carried
by wind from the southern continents to Antarctica changed considerably
as the Earth's climate changed.

"The terrestrial dust coming down on Antarctica during the Ice Age
obviously is not the same as that during warm periods," said Gisela
Winckler, a Doherty associate research scientist at Lamont-Doherty and
lead author on the study. "This may be due to the mineral dust
originating from different regional sources or to changes in the process
responsible for producing the dust."

The project was supported by the Comer Science and Education Foundation.

About the Lamont-Doherty Earth Observatory

The Lamont-Doherty Earth Observatory, a member of The Earth Institute at
Columbia University, is one of the world's leading research centers
seeking fundamental knowledge about the origin, evolution and future of
the natural world. More than 300 research scientists study the planet
from its deepest interior to the outer reaches of its atmosphere, on
every continent and in every ocean. From global climate change to
earthquakes, volcanoes, nonrenewable resources, environmental hazards
and beyond, Observatory scientists provide a rational basis for the
difficult choices facing humankind in the planet's stewardship. For more
information, visit www.ldeo.columbia.edu .

About The Earth Institute

The Earth Institute at Columbia University is the world's leading
academic center for the integrated study of Earth, its environment and
society. The Earth Institute builds upon excellence in the core
disciplines - earth sciences, biological sciences, engineering sciences,
social sciences and health sciences - and stresses cross-disciplinary
approaches to complex problems. Through research, training and global
partnerships, it mobilizes science and technology to advance sustainable
development, while placing special emphasis on the needs of the world's
poor. For more information, visit www.earth.columbia.edu .
Received on Fri 04 Aug 2006 12:53:22 PM PDT