24 June 2011

Termination of the NEEM 2011 Shallow Core 1 (S1) drilling

Celebration of 400 m depth for the S1 core in front of the sauna tent

Due to logistical constraints the drilling of the S1 borehole in the sauna tent terminated this night at 11 pm at a depth of 411.83 m, which corresponds to an age slightly older than 79 AD. THANKS AND CONGRATULATIONS to all drillers who participated in this effort that turned out somewhat more challenging than anticipated: At quite shallow depth core breaks became unpleasantly hard. At some point the winch motor burned and the full cable had to be pulled of the cable drum in the snow for mounting of a spare motor. This exercise was repeated when also the spare motor burned, and some innovation was required to mount a different type of motor that was kindly provided by our AWI colleagues. Then at around 275 m depth the core quality suddenly decreased significantly with an almost regular pattern of internal cracks and breaks appearing in the core. After quite some trial and error, it was somewhat surprisingly realized that the main cause of the core breaks was the low liquid stand in the bore hole. As more liquid was added to the hole at a drilling depth of 292 m the core quality instantly improved and it has generally been good since then. Then drill tent temperatures close to the melting point disallowed drilling for a short period. Just to top off the list of complications the core barrel was lost in borehole a couple of times. One case was non-trivial and the core barrel stayed at the bottom of the hole for a scaring 12 hours until it could be recovered. Thanks to their hard work and high morality the drillers got it all sorted out. The drill is safe back on surface, and the deepest part of the core is now being split and packed in the science trench for shipment to DRI (Joe McConnell) for continuous aerosol and multi-tracer measurements and to LGGE (Jérôme Chappellaz) for detailed CO analysis.

What we have done today:
1.  NEEM S1 final drilling depth 411.83 m
2.  CFA of brittle zone: bag 1381 – 1546 (759.00 - 850.30) 15.4 m analyzed. 17%
3.  NEEM S1 ice core processing: bag 624 – 691 (342.65 - 380.05 m)
4.  Continued AWI radar grid measurements. Re-measuring sections of data loss
5.  Worked on connecting new AWI drill to DK 1000m winch
6.  Checked skiway. It is currently in good conditions for next weeks flights

Ad. 2: The core quality is getting increasingly poor and from time to time entire sections of 1.10 m sample have to be skipped as they contain no unbroken segments. Today the CFA temperature stabilization system caused some disturbance for the dayshift.

Ad. 3: The core processing had a record day of 37.4 m processed today!

Weather: Mostly overcast, some snow showers, and a little snow drift. Temp. -7 °C to -12 °C, wind 8 - 16 knots from S.

FL, Anders Svensson

The entire drill team waiting for the 400m core to come up: Christopher, Darcy, Andrew, Sune, Steff, Bo, and Li

Bo, Yoshi, Antje, and Catherine are marking plastic bags for packing of the S2 ice core. But why the funnel, Yoshi?

On the CFA nightshift melting their way through the rapidly diminishing fraction of unbroken sample in the main core brittle-zone 

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