Research Objectives:
The summit crater of Mount Moulton contains a 600-meter-thick, horizontally exposed section of ice with intercalated tephra layers from nearby Mount Berlin. Argon-40/argon-39 dating of the thick, near-source tephra indicates that the age of the horizontal ice section ranges between 15,000 and 492,000 years. Thus, the Mount Moulton site offers an unparalleled repository of ancient West Antarctic snow and trapped air that can be used to investigate climate over much of the past 500,000 years. The planar nature and consistent dips of the tephra layers suggest that although the ice section has thinned, it is otherwise undeformed.
We visited the Mount Moulton site during the 1999–2000 field season, at which time we collected a horizontal core representing approximately 400 meters of ice, ranging from 15,000 to more than 480,000 years old. In addition to this horizontal core, we took samples at various depths to test the quality of the climate record in the ice. We also collected 40 intercalated tephra layers to provide a chronology for the ice section. The results of this first effort are extremely encouraging. There is clearly a usable record of past climate extending back beyond 140,000 years.
There is work to do, however, to realize the full potential of this horizontal ice core. The elemental and isotopic composition of trapped gases suggests some contamination by modern air. Since gas cross-dating of ice cores is the current standard by which climate records are compared, we need to understand why and how the gas record is compromised before adding Mount Moulton to our arsenal of ice-core paleoclimate records.
Our research has the following objectives:
+ To evaluate more thoroughly the integrity of the climatic record through shallow drilling of blue ice, as well as the snow field upslope from this area;
+ To improve the radioisotopic dating of specific tephra layers;
+ To obtain baseline information about modern snowfall deposition, mean annual temperature, and wind pumping around the summit of Mount Moulton; and
+ To study how firn densification differs when surface accumulation changes from net accumulation to net ablation.
