We begin an unpleasant task
Processors, Maibritt, Marie and Peter, are preparing bags for brittle zone processing.
Ice is compressed snow. It is full of bubbles of air trapped between the original snow crystals. It is this air that provides the global society with valuable and unique information on the content of green house gases in the atmosphere in past climates. The air in the bubbles undergoes compression as the ice layers sink, because pressure increases with depth in ice, just as in the ocean. In ice the pressure increases by 9 bar each 100 m depth. In 600 m depth, the pressure is close to 50 bar, and this pressure is so high, that the ice cannot withstand the strain. Spontaneous cracks are formed. We say, the ice is brittle. Ice from even greater depths is even more brittle; but nature is helpful. When pressure reaches 90 bar, the air is literary squeezed out of the bubbles and slides into the ice crystals, where the air molecules form a special chemical compound with the ice called chlathrate-hydrates, or crystal-water. The bubbles gradually disappear and at 1200 m depth, they are gone. The ice core is now crystal clear and strong. The depth interval between 600m and 1200 m is called the “brittle-zone”.
What we have done today:
- Drilling and logging.
- Processing ice cores.
- Removing snow drifts around storage garage..
- Measuring CFA. All analyses are working. Today we measured 19.8 m. Last bag 2469, 1357.95 m
- Making special handling tools for processing brittle core.
Promising day in the drill trench with a production of 15.34 meters. Pressure tube “2” is now in service and produced two full runs to end the evening with good chip recovery. Lower current is used to drill with this motor section with runs proceeding with 7 to 9 amps rather than 10 to 12 (or current limitation) with a similar set up using pressure tube “1”. The hollow shaft configuration is set exactly to how we ended last season. In all cases a clean hole and a clean hollow shaft seem to be a requirement for good drilling, as short runs today seemed to be plagued by extra chips in the borehole.
Drillers depth: 1851.34 m
Weather: Thin overcast and fog/haze, in the evening clearing. -20°C to -13°C, 15-18 knots from S, in the evening 4 knots from SSW. Visibility: Between 3 miles and unrestricted.
FL, J.P. Steffensen
At the end of the science trench, in a quiet corner, Sepp studies the crystal structure of the ice.
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