The West Antarctic Ice Sheet (WAIS) Divide ice core project is a United States deep ice coring project in West Antarctica funded by the National Science Foundation. On December 1, 2011, the WAIS Divide ice core project 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.
Ice core science has dramatically advanced our understanding of how the Earth's climate has changed in the past. Ice cores collected from Greenland have revolutionized our notion of climate variability during the past 100,000 years. The WAIS Divide ice core is the highest resolution, best dated ice core record from Antarctica. As such, the WAIS Divide ice core is providing 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 cores.
What makes the WAIS Divide ice core special?
- The WAIS Divide ice core is the highest resolution, best dated ice core record from Antarctica to date. The ice core record extends back in time 68,000 years.
- The most significant and unique characteristic of the WAIS Divide project is the development of climate records with an absolute, annual-layer-counted chronology for the most recent ~30,000 years.
- The ice that is between 30,000 and 68,000 years old still contains a higher time-resolution record than previous Antarctic ice cores.
- Because the snowfall rate at WAIS Divide is so high, we are able to get exquisitely detailed data, showing very clearly how carbon dioxide and methane variations are linked to temperature changes in the southern and northern hemispheres.
- The gas records from WAIS Divide are particularly significant because the age difference between the gas and the enclosing ice (and the uncertainty in this value) is very low, due to the high snowfall rate. Because of this small age difference between the gases and the enclosing ice, a decadal-precision climate chronology relative to the Greenland ice cores is possible.
- The combination of high-time resolution and the small age offset allows us to study interactions between climate variations and atmospheric composition with a level of detail previously not possible in deep long Antarctic ice core records.
- Unlike the Greenland ice cores, the WAIS Divide ice core contains an excellent atmospheric carbon dioxide record, since Antarctic ice has an order of magnitude less dust than Greenland ice.
- Many other gases (both greenhouse and non-greenhouse) and their isotopes are being measured at unprecedented precision and resolution.
What is an ice divide?
An ice divide is analogous to a watershed divide. An ice sheet divide separates opposing flow directions of ice on an ice sheet.
Why do we want to drill near an ice divide?
Snow and ice that accumulates on an ice divide moves vertically downward with time. As you move laterally off of an ice divide the ice increasingly moves horizontally. Irregularities in the bedrock below the ice sheet can cause horizontally moving layers of ice to bend and fold thus disturbing the internal layering of the ice. Ice coring is typically made on top of ice divides to minimize these potential interferences in the stratigraphic record caused by horizontal ice movement. The WAIS Divide deep ice core drill site is actually ~24 kilometers downslope of the current ice divide because ice divides can migrate over time. Drilling slightly off of the current ice divide helps ensure that no divide migration has compromised the stratigraphy of the ice core record.
Why WAIS Divide?
The WAIS Divide site was chosen because it is an almost exact analogue to the GISP2 ice core in Greenland in terms of accumulation rate, temperature, gas age-ice age difference, and distance from the ice divide.
Main science objectives:
- Develop the most detailed record of greenhouse gases possible for the last 68,000 years
- Determine if the climate changes that occurred during the last 68,000 years were initiated by changes in the northern or southern hemisphere
- Investigate the past and future stability of the West Antarctic Ice Sheet
- Investigate the biology of deep ice