Drilling a vertical hole through the Filchner Ice Shelf measuring only 30 centimetres wide but 900 metres deep would theoretically require more than 60 cubic metres of hot water – a tremendous amount, especially given the fact that all of the water on the shelf is frozen solid. To be able to drill nonetheless, researchers have a trick up their sleeve: melting the water they need for drilling right on top of the ice shelf. In the following, AWI engineer Jörg Brozek explains in detail how the process works.
First of all, we prepare the starting water (image 1). To do so, we melt a small amount of snow and heat it to 95 degrees Celsius. We then keep adding snow bit by bit, until we’ve made 10 cubic metres of hot water.
Everyone knows that liquid water seeps into snow. So we use the starting water and bore to a depth of roughly 100 metres, a point at which the firn has transformed into ice. We then use the rest of the starting water to carve out a cavern (image 2). We make the cavern part of the drilling-water circuit, allowing us to continuously melt new drilling water in the ice, which we then pump to the surface and heat up.
To make sure we don’t damage the equipment used in the cavern, the next step is to drill a second hole roughly 50 centimetres away from the first one (image 3). This is the main borehole, and also passes through the cavern.
To ensure the cavern doesn’t “run dry” when the main borehole (image 4) breaks through the ice shelf, it has to be made below sea level.
Thanks to this method, we have a practically unlimited supply of drilling water, which we later use to expand the main borehole, making it large enough for conducting our planned experiments and anchoring thermistor chains (image 5).