Scientists have had their first inside look at ice
layers, frozen debris and a surprising channel of water deep
beneath an Antarctic ice stream, thanks to an ice probe
designed by NASA’s Jet Propulsion Laboratory, Pasadena, Calif.
Plunged more than 1,200 meters (more than 3,900 feet)
down four boreholes drilled in the West Antarctic ice sheet,
JPL’s probe paves the way for the development of technology
capable of withstanding extreme environments on Earth and
other planets.
The Antarctic Ice Borehole Probe Project, a collaborative
effort of scientists at JPL and the California Institute of
Technology in Pasadena, looked into the dynamics of the West
Antarctic ice sheet. The Antarctic ice sheet, equal in size
to the United States and Mexico combined, holds a potential
treasure trove of information related to the geological
history of this frozen continent and the mechanisms by which
ice flows from this area to the oceans. Studies show that
significant changes in glacier melting and flow rates could
have a considerable impact on global sea levels.
“This project fits into the bigger picture of planetary
studies,” said Dr. Frank Carsey, JPL’s principal investigator
on the project. “It provides us with some understanding of
how to observe what goes on deep in ice caps — Earth’s ice
caps, Martian ice caps and ice caps on Europa.” Europa is an
ice-covered moon of Jupiter.
The glaciological investigation took place at Ice Stream
C, an area in the West Antarctic ice sheet where 150 years ago
the ice suddenly stopped flowing in one area in the lower part
of the stream. This so-called “sticky spot,” currently
flowing at a rate of 2 meters per year (about 6 feet), greatly
differs from its neighboring streams, flowing at approximately
400 meters (1,300 feet) per year.
Equipped with two cameras and lights, JPL’s ice probe
revealed what appears to be a basal water system, or series of
water channels at the base of the ice stream. In places, this
water-filled cavity measured approximately 1.4 meters deep
(4.6 feet). Based on previous calculations, researchers
expected the depth of a water basal cavity to be only in the
millimeter range.
To the researchers’ surprise, they also found rock and
other debris embedded in the ice much higher than expected.
It was believed that frozen debris would be found no higher
than two meters (almost seven feet) off the base of the ice
stream. In contrast, the visual data shows frozen debris some
26 meters (85 feet) off the base, which has yet to be
explained.
A layering effect in the ice was also uncovered by the
probe. Though not yet fully understood, it is thought that,
upstream, ice and gravel have frozen onto the base of the ice
sheet. With the ice streams constantly moving, water may
slide under debris-laden layers, lifting them up, allowing the
process to repeat.
“The layered information will turn out to be very
interesting,” said Carsey. “These layers tell us about
processes upstream.” By analyzing these ice layers,
researchers may learn how ice streams flow and stop flowing.
The team’s findings open up the doors to further
glaciological research. “With the probe, we have now left the
dark ages,” said Hermann Engelhardt, Caltech’s principal
investigator on the project.
JPL hopes to advance the probe’s technology in the next
year or two, adding biological sensors to search for evidence
of life in the Antarctic ice sheet and eventually on other
planets. Microbes are known to reside under mountain
glaciers, where it is warmer and there are nutrients from
impurities found between water crystals.
“These locations are very old places. Some, such as on
Mars, are hundreds of millions of years old,” said Carsey.
The base of a planet’s polar cap chronicles the planet’s
climate and can reveal much about its history and biology, he
said.
Images of the team’s findings are available at
http://www.jpl.nasa.gov/pictures/iceprobe .
The Antarctic Ice Borehole Probe Project is a
collaborative effort of JPL and Caltech, supported by NASA,
Washington D.C., and the National Science Foundation,
Arlington, Va. The ice probe was developed by JPL, a division
of Caltech.
