28 July 2009

The beauty of ice crystals

10.000 year old ice crystals

Beautiful ice crystals from 10.000 year old NEEM ice.

A less than 0.5mm thin slice of ice placed between polarized light reveal the single ice crystals in the ice core.  The picture represents a section of an ice core placed horizontally. The beautiful colors tell us that the crystals have very different c-axis orientation. Observe the band of smaller crystals to the left of the picture which probably is a band of ice with a high concentration of impurities from a spring storm 10.000 years ago which reduces the crystal growth rate.

What we have done today:

1.Drilling with the NEEM long drill: 23.29 m. Drillers depth: 1401.66 m
2. Logging 23.48 m of core. Logging depth 1411.47 m
3. CFA analysis: 17.05 m. Depth: 567.05 m.
4. Processing 21.45 m. Processing depth: 1377.20 m (bag 2504)
5. Shallow drilling at the second site NEEM2009S1. Depth 136 m
6. Packing in the firn-village
7. Collecting cargo on pallets.

Ad 1: Drillers report 28 July: “A good day drilling ending with three runs with a new drill head.  Cutting pitch of 2.1 mm gives motor current of 8.5-9 amps for the first 2.2 meters of each run followed by 11 to 11.5 amps for the remaining 1.3 meters of the 3.5 meter ice cores.  The chips remain mainly in the lower half of the chip chamber.  Inclination held steady today at 2.65 degrees.  We have the first signs of a very small amount of chips on top of the cores. Bottom density of liquid is 922 at -24°C;.”

Ad 2: The logging is eagerly followed to find the glacial-interglacial transition. We have seen no visible sign of the transition yet – the truth will come when the ice is processed in the science trench.

Ad 4: The processing of bag 2500 was celebrated in the science trench.

Ad 5: The core quality is too poor to continue drilling in the NEEM2009 S1 borehole at the depth 136m. The ice core is drilled with the 3 inch shallow ice core drill without the use of drill liquid.

Weather: Overcast with light snow. From time to time the overcast was broken with big spots of blue sky. Wind 10kn decreasing to 3 kn from W to SW. Temperatures -10°C to -7°C.

Recording the ice crystals on the laptop
Daphne recording the ice crystals on the laptop in the physical property laboratory in the science trench.

Bag 2500 has been processed
Celebration of the processing of bag 2500 in the science trench

FL, Dorthe Dahl-Jensen

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