On December 1, 2011, the West Antarctic Ice Sheet (WAIS) Divide ice core project, funded by the National Science Foundation (NSF), reached its final depth of 3405 meters (11,171 feet; over 2 miles), recovering the longest U.S. ice core to date from the polar regions. The 12.2-centimeter (4.8-inch) diameter cylinders of ice that make up the ice core contain uniquely detailed information on past environmental conditions during the last 68,000 years, such as the atmospheric concentration of greenhouse gases, surface air temperature, wind patterns, the extent of sea ice around Antarctica, and the average temperature of the ocean.
Successfully retrieving the ice core is the culmination of an eight-year project to obtain a paleoclimate record from one of the remotest parts of the Antarctic continent.
The WAIS Divide ice core was recovered at a field camp in the center of West Antarctica, 1,040 kilometers (650 miles) from the geographic South Pole, where the ice is more than 3,460 meters (two miles) thick. The drill site is at an ice divide (which is analogous to a watershed divide), where the ice is flowing out to the sea in opposing directions. The drilling of the ice core ceased 100 meters (328 feet) above the contact between the ice and the underlying rock, to avoid contaminating a possible water layer at the ice-rock contact. The basal water system may consist of water-saturated, ground-up rock, and has not been exposed to the earth's surface for millions of years. It may harbor a unique and pristine biological environment that the U.S. scientific community does not wish to contaminate.
In the WAIS Divide ice core, each of the past 30,000 years of snowfall can be identified in individual layers of ice, with lower temporal resolution records extending to 68,000 years before present. By allowing an examination of past climate at an annual resolution, the ice core record is helping scientists understand why climate can change abruptly and how climate may unfold in the coming century.
Other ice-coring projects have produced cores of lower temporal resolution, showing that the current level of atmospheric greenhouse gases, which is due to the burning of fossil fuels, is the highest in at least 800,000 years. The ice from the WAIS Divide ice core that is between 30,000 and 68,000 years old — while not containing records with annual resolution — contains a higher time resolution record than previous projects.
When snow falls at WAIS Divide it rarely melts, and instead builds up in thick annual layers, which are compressed into ice by subsequent snowfall. The ice layers contain dissolved chemicals, insoluble dust particles, and atmospheric gases that were present when the snow fell. The age of the ice is determined by identifying the chemical and physical difference between winter snow and summer snow, and counting the years is much like counting tree rings to determine the age of a tree. By drilling down into the ice sheet and recovering ice from ancient times it is possible to determine the climate conditions when the snow fell. The ice layers contain a record of how the climate changed. This allows scientists to determine how and why climate changed in the past. By understanding how and why climate changed in the past, scientists are able to improve predictions of how climate will change in the future. Ice cores also help scientists understand how the size of the ice sheet has changed in the past in response to different climate conditions, which helps scientists predict how the ice sheet will respond to future climate changes.
The 12.2-centimeter diameter 3405-meter-long ice core is cut into 1 meter (3 feet)-long pieces of ice and is stored at the National Ice Core Laboratory in Denver, Colorado, USA. Samples of the WAIS Divide ice core have been distributed to more than 20 U.S. university and national laboratories around the U.S., who make the measurements.
The WAIS Divide ice core has provided the first Southern Hemisphere climate and greenhouse gas records of comparable time resolution and duration to the Greenland ice cores, enabling detailed comparison of environmental conditions between the northern and southern hemispheres, and the study of greenhouse gas concentrations in the paleo-atmosphere, with a greater level of detail than previously possible. The WAIS Divide ice core is also being used to test models of WAIS history and stability, and to investigate the biological signals contained in deep Antarctic ice.
NSF's Division of Polar Programs funds the research, primarily through its Antarctic Glaciology Program. Some additional funding is provided by NSF's Antarctic Organisms and Ecosystems Program. Logistical support is from NSF's Divisions of Antarctic Infrastructure and Logistics. The Ice Drilling Program Office and Ice Drilling Design and Operations group designed the drill and conducted the drilling. The National Ice Core Laboratory (NICL) designed and built the core handling systems at WAIS Divide and at NICL, and curates the archived ice core. The lead scientific institution is the Desert Research Institute, Nevada System of Higher Education, and the Chief Scientist is Dr. Kendrick Taylor. Science coordination is provided by the University of New Hampshire.