The Thermal Probe Deep-Drilling Method by EGIG in 1968 at Station Jarl-Joset, Central Greenland

A special thermal probe deep-drilling method was used by Expedition Glaciologique Internationale au Groenland (EGIG) 1968. The wire for the transmission of the electric power and the measured values pays out of the probe and becomes fixed in the refreezing meltwater.

Two probes were constructed, each with a diameter of 10.8 cm and lengths of about 2.5 m (probe II) and 3 m (probe I). With the available maximum power of 3.7 kW the velocity was 2 m/hr.

The probes had sufficient wire for the penetration of the ice sheet (2500 m), but the breakdown of the main heater stopped probe I at a depth of 218 m and probe II at a depth of 1005 m. The ice temperatures recorded after cooling occurred were: -29.0°C at 218 m, -29.3°C at 615 m and -30.0°C at 1005 m depth. The method as such worked without significant problems.

Thermal probes of this type are relatively inexpensive (about $15,000), easy to handle (about 10 cm diameter, 200-300 cm length) and work fast (50-100 m/day or more). A small summer expedition could penetrate 4000 m of ice or more.