Impact #361 ARE POLAR ICE SHEETS

• Main Authors: Only Years Old, Michael J. Oard
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2003
• Subjects: Antarctic; Greenland; Antarc*; Antarctica; GRIP; Ice Sheet
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.174.1650; http://www.icr.org/i/pdf/imp/imp-361.pdf

Glaciologists have drilled about a dozen deep ice cores into the Greenland and Antarctic Ice Sheets. The two most important, drilled to about 3000 meters to bedrock from the top of the Greenland Ice Sheet, are the GRIP and GISP2 cores. 1 It is claimed that annual layers of snow and ice, so well marked at the top of the cores, can be counted downward to 2800 meters for a total of 110,000 years in the GISP2 core. 2,3 The annual layer method is said to be like counting tree rings to determine the age of a tree. (The measurements could not be made below 2800 meters because the annual layer thickness was assumed to be too thin. The 250 meters of ice below this depth is believed to be many hundreds of thousands of years old.) The focus of drilling has recently shifted to Antarctica where several deep cores to over 3000 meters have been drilled. The most important is the new Vostok core that reached 3623 meters in 1998 but stopped drilling due to the presence of a lake 120 meters deeper. The Vostok core is said to span 420,000 years through a depth of 3310 meters. 4