5 July 2010

Drilling the 'warm ice'

Happy Birthday!
Paul's birthday celebrated today with nice cake and something Austral-Italian.

The ice core currently retrieved at NEEM is ‘warm' in two ways: Most likely it is deposited in a climatically warm period, so it is ‘warm' in its water isotopic composition. The actual temperature of the ice at the bottom of the borehole is also ‘warm', probably around -7 °C, due to the geothermal heat flux that heats the ice sheet from below.

Both types of warm conditions favour large ice crystals, which generally makes it more difficult to break the core when the drill is pulled up. Just today there was a hard core break and large crystal boundaries are clearly visible in most core breaks. Ice close to the pressure melting point can also lead to melting at the drill head due to friction heat, which - in worst case - can get the drill stuck (let it never happen!). Other potential troubles the drillers may face are non-engaging core catchers (the knives that breaks the core when the drill is pulled up) that leaves the ice core at the bottom when the drill goes up and ice packing on the ‘shoes' below the knives so that the drill does not penetrate the ice.

In general, however, the drilling is progressing very well, the ice core quality is excellent and the drilled cores are normally 3+ m long, so we cross our fingers that it will continue like that all the way to bedrock, which is expected in approximately 160 m.

Drilling: 14.41 m, drillers depth: 2364.01 m.
Logging: 14.20 m, loggers depth: 2380.15 m.
Processing: bag 4250-4313 (35.20 m) 2372.15 m.
CFA: bag 3550-3589 (22.00 m) 1973.95 m.

What we have done today:
1. Drilling and core logging ice.
2. Processed deep ice cores.
3. CFA measurements.
4. Maintained Pistenbully.
5. Moved 2nd core buffer forward.
6. Put up tent on small trench elevator.

Weather: Clear blue sky, low winds from SE and temperatures -16 °C to -5 °C.

FL's Dorthe Dahl-Jensen and Anders Svensson


← Previous entry   Next entry →