Ice Core Recovery
Six cores, totaling 623 meters, were drilled at the sites shown in the figure. Core 1, the longest, was drilled 460 meters to bedrock. This is the deepest ice core to be recovered from an alpine ice field. The 10-meter ice temperature was -24o C and the temperature at 460 meters was -19.8oC; therefore, the col of Bona-Churchill is a cold based glacier. Core 2 was 114 meters long and was complemented by four shallow cores ranging from 10 to 12 meters in length. These were drilled in a diamond-shaped configuration across the col. The short cores were recovered to determine the impact of drifting on the various chemical and physical signals preserved in the ice strata and to assess the reproducibility of the records from the col. These shallow cores, along with the two deep cores, will allow characterization of the spatial distribution of annual snow accumulation (An) across the col. A single pulse radar-sounding unit was used to measure bedrock depths at 34 sites across the col, and these data were used to prepare an ice thickness map. The surface was mapped using GPS and an electronic altimeter.
|Photo by Vladimir Mikhalenko||Photo by Lonnie Thompson|