REPLICATE CORING, BOREHOLE LOGGING, BASAL SCIENCE
The WAIS Divide science and implementation plan, the funded proposal to build the drill, and the funded proposal to conduct field operations, all call for replicate coring to recover additional ice from depth intervals of special interest, borehole logging, and basal sampling of basal water and geologic material.
During the 2007 WAIS Divide science meeting, two groups were formed to investigate: (i) replicate coring and borehole logging, and (ii) basal sampling. The replicate coring and borehole logging group consisted of Ed Brook, Erin Pettit, Jinho Ahn, and Todd Sowers. The basal sampling group consisted of John Priscu, Mark Skidmore, and Slawek Tulacyk. Each group was tasked with developing a science and implementation plan, one for replicate coring and borehole logging, and one for basal sampling. The two science and implementation plans were drafted in 2008, input from the community was solicited, and the two plans were subsequently submitted to the WAIS Divide Executive Committee for review.
During the 2008 WAIS Divide science meeting, the Executive Committee discussed the Replicate Coring and Borehole Logging Science and Implementation Plan and voted to endorse the plan. The plan was subsequently forwarded to NSF and IDPO-IDDO, and Jeff Severinghaus was encouraged to seek funding for the activity. The Executive Committee also discussed the WAIS Divide Basal Science and Implementation Plan, and voted to not endorse the plan at the time. The general concept of the plan had support, but some details needed more attention. The Executive Committee made numerous suggestions to the authors and asked them to resubmit the plan to the Executive Committee.
After reviewing the revised Basal Sampling Science and Implementation Plan, the WAIS Divide Executive Committee, in consultation with the WAIS Divide Community, advised NSF that basal sampling was not a priority for the WAIS Divide project because the basal sampling science objectives would be better met with different drilling methods at different locations by the proposed, and subsequently funded, Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project. As a result, basal sampling at WAIS Divide was pursued no further.
In 2010, Jeff Severinghaus, Jihong Cole-Dai, and Ed Brook submitted a proposal to NSF to conduct replicate coring at WAIS Divide to obtain additional samples at events of high scientific interest, and NSF subsequently funded the proposal. The replicate coring technique, developed and tested by Ice Drilling Design and Operations (IDDO) as part of the Deep Ice Sheet Coring (DISC) drill, is a key advance, because it allows scientists to take samples from specific levels of a parent borehole without impeding the hole itself, leaving the parent borehole open for future logging of information. After testing the replicate coring system at the end of the 2011/12 field season, the system was deployed in December 2012 to re-enter the deep borehole, and successfully allowed the researchers to drill through the wall of the 3405-meter deep parent hole and collect a total of 285 meters of additional core from five of the most interesting time periods in the WAIS Divide climate record.
Logging of the WAIS Divide deep borehole was conducted during the 2011/12 (temperature, sonic, optical, and seismic logging) and 2014/15 (temperature, optical, televiewer/borehole deformation, and seismic logging) field seasons.