Researchers spent 2 months this summer high in the Peruvian Andes, and brought back two cores, the longest ever drilled from ice fields in the tropics.
State glaciologist Lonnie Thompson says that this latest expedition focused on
a yet-to-be-named ice field 17,598 feet above sea level in the Cordillera
Blanca mountain range.
researchers hiked to a col, or saddle, between two adjacent peaks – Hualcán and
Copa – set-up camp, and used a ground-sensing radar to map the ice depths
across the glacier. They then drilled two cores through the thickest part of
the ancient ice to bedrock, capturing the entire climate record at this site.
of the cores measured 643 feet, while the other totaled 620 feet. Thompson says
that the initial visual inspection of the cores showed that they contained a
number of insects and plant materials that may have blown up onto the glacier
from the Amazon Basin. "I've never seen so many of what appear to be
plants and insects in any of the ice cores we've previously drilled," he reveals.
"We should be able to identify them and use carbon-14 to date them.
will help us determine the age of the ice in the core. These cores also contain
very distinct bubble-free, or clear, ice near the bottom, which suggests very
warm conditions in the past. The cores only arrived back to the freezers at OSU
a few weeks ago so we have lots of work to do."
a professor of earth sciences at Ohio State and research scientist at the Byrd
Polar Research Center, says that his team did a preliminary analysis for oxygen
isotopes and dust particles from a 33-foot section of the core. These results
confirmed that the core contains an annually resolvable record of the climate
conditions at the site. The ratio of oxygen isotopes in the ice allows
researchers to determine whether temperatures were warmer or cooler when the
snow that eventually turned to ice was deposited on the glacier. The dust content
gives scientists clues about the rate of precipitation at the site.
was the last opportunity anyone will have to drill at this site," Thompson
explains. "The warming temperatures there cause melting that compromises
the quality of records preserved in the ice. Any future drilling efforts will
have to be at colder, and higher, elevations to minimize the impact of melting
that can obscure the climate record. Unfortunately, there are very few good
drill sites above [17,598] in the Cordillera Blanca."
Newly Drilled Ice Cores from the Andes
November 9, 2009