Replicate coring is the act of deviating out of an existing borehole to collect additional ice samples from depth intervals of particular interest.
Replication of results is fundamental to science, and the ability to obtain additional ice samples from "intervals of scientific interest" will aid in the replication and verification of key results from ice core science. In addition, within a given ice core, scientific demand for ice samples is very unevenly distributed, with the ice core archive being completely depleted in depth intervals of high scientific interest. Replicate coring allows scientists to obtain additional ice samples from intervals of high scientific interest without needing to re-locate the drill to bore another hole.
The Replicate Ice Coring System collects additional ice at depths of interest by deploying into an existing borehole and then deviating from it. The drill uses two steering actuator sections to tilt itself in the parent borehole by applying sidewards force against the borehole wall. The sidewards force causes the drill to preferentially "cut" into the "up hill" side of the borehole wall with a broaching head. The process of preferentially broaching the "up hill" side of the borehole wall is repeated until a separate borehole is created. The broaching head is then replaced with a coring head, the actuators tilt and guide the drill into the replicate borehole, and additional ice samples are collected via traditional ice coring.
The Replicate Ice Coring System will be field-tested at the West Antarctic Ice Sheet (WAIS) Divide deep ice coring site in Antarctica in January 2012. Production drilling with the system is planned for the 2012-2013 Antarctic field season at WAIS Divide.
The Replicate Ice Coring System is designed to be used with the Deep Ice Sheet Coring (DISC) Drill and thus requires substantial logistics and infrastructure support. However, the design and engineering behind the system is such that it can be scaled down for use with smaller, more agile drilling systems as well.
For more information about the Replicate Ice Coring System, as well as other ice drilling equipment available to the U.S. ice science community, visit:
Figures courtesy of Chris Gibson, Lead Mechanical Engineer, Replicate Ice Coring System, Ice Drilling Design and Operations (Univ. Wisconsin-Madison)
The U.S. Ice Drilling Program maintains and operates existing ice drilling equipment and develops new systems with two principal foci:
- to provide high quality ice cores, and
- to produce boreholes that provide access to the interior and beds of ice sheets and glaciers for such purposes as embedding instruments, collecting gas samples, setting seismic charges, and studying subglacial processes.