Drilling on land has its counterpart. If drilling work is to be carried out on a blanket of ice, an ice core drilling process can be employed. There are several drill techniques currently used for this purpose considering the fact that drilling through solid ice is a pretty arduous task.
Most ice drilling projects involve getting through the oldest ice. Hence, drilling through the ice to reach its core, near the ice divide, is done. Ice divides are usually located at some distance, far away from the ocean and research bases.
For purposes of education on this subject, here are some of the employed drilling techniques used in ice drilling.
The Hand Auger
Of all the drill systems available in the industry today this, by far, is considered by those involved in the business as the simplest and the lightest of them all. It is capable of collecting 74 mm diameter core from the surface of 10-meter firn (firn – this is a phase between ice and snow). The drill itself consists of an ice-cutter containing a drill head that takes on the job of drilling into the firn. The core barrel, responsible for holding the core intact upon pulling to surface, connects the rods so they will extend to a depth of at least 10 meters.
The entire system can be held inside 2 relatively easy-to-carry boxes, each box weighing about 80 kg. This allows for easy deployment with, say, a small aircraft.
The drill will cut away a ring off the firn while rotating, and by virtue of the natural gravity, it will descend deeper and deeper. And as it goes deeper, it will fill the central cavity with an unblemished firn core. The operator can pull the core barrel up to the surface when it is already full. After 15 “runs”, it will have a total of 10 meters long and 74 mm diameter firn core would have been brought to the surface. The cores, upon completion, will be fitted together, labeled, measured. Later on, they will be packed inside custom ice core boxes, ready for shipping back to a lab for further analysis.
The Shallow Drill
In terms of their sizes, a shallow drill system is considerably heavier, larger, and more complex. Deploying a complete setup, together with spares, tools, and a power generator system, everything will weigh around 800 kg. The weight is estimated to go around 10 times the hand auger. You can place a shallow drill on 2 Nansen sledges and it can be towed using a ski-doo. A small plane also can be used if you want to transport them to what can be considered as less accessible drill locations.
Much like the hand auger, this type of ice drilling system collects at least a minimum of 74 mm diameter core, starting at 2 meters below the ground surface. As for the descent, it would be a maximum of 350 meters down.
We qualify this drill technique for ice core as an electromechanical drill, raised and lowered by an electrical winch. The surface’s tilting tower will help in easing drill handling and core extraction.
As for the drill head and core barrel, they share a certain level of similarity to the hand auger on this aspect. However, the core barrel is usually contained within another outer core barrel, but this will never rotate, though, while drilling work is in progress. Vertical grooves found lining the outer core and thick spirals on the outside significantly help in transporting the chippings of drilled ice to the core barrel top part. From here they will be contained inside a plastic insert at the top of the core. The drilled core segments measure up to 1 meter in length.
Success in ice core drilling lies in the effective use of known drilling techniques. The most widely used ones took several decades to develop and were built based on the experience, knowledge and hard work of many people. Different kinds of drills may be required when working on varying drilling depths since conditions are likely to change with respect to depth through the ice cap.