12 August 2009

Ice from the Last Glacial Maximum


Vasilis and Christopher prepared the carefully cleaned slabs of ice for the linescan and run the instrument. The images in the cold glacial ice are stripped with clear and cloudy bands.

The ice being processed in the science trench is 30.000 years old from the deep Last Glacial Maximum when it was 25°C colder in Greenland than at present. The line scan images are recordings of the visible features seen through a cleaned slab of ice in indirect light. The ice is stripped with clear and cloudy bands. The cloudy bands appear white while the clear ice appears black on the line scan image. The cloudy bands coincidence with layers of high impurity concentrations mainly from the spring storms each year 30.000 years ago. The annual layer thickness is around 1.2 cm here.

What we have done today:

1. Drilling with the NEEM long drill: 29.00 m. Drillers depth: 1705.04 m
2. Logging 2.45 m of core. Logging depth 1713.29 m
3. CFA analysis: 4.40m, From Final CFA depth 1295.25 m (bag 2355)
4. Processing 28.05 m of core. Processing depth: 1669.25 m ( 3035 bag )
5. Lowering and leveling snow around the main dome
6. Making new box for white weatherport
7. Finalized making order and documenting the storage garage.
Documentation is in ‘Lagerlisten’
8. Building a pallet of empty drums
9. Placing pallets on the surface for building of new pallets

Ad 1,2: It has been noted that the drillers length (cable length) and the loggers length (summed core length) has diverged from the expected 12 to 13 m to 17.5 m. After careful investigation of the evolution of the difference and the logging and cable length measurements it is concluded that the logging is up to the standard and the difference to first order is caused by dirt collecting on the wheel that measures the cable length.

Ad 3: The CFA lab closed today after measuring the first 25 bags of ice below the brittle zone. During the last weeks there has been increasing problems with the very complicated systems and the whole team is relived that it now is time to pack and take the equipment home for cleaning and repair.

Weather: Ice fog lifted at 05:00 and we had a day with overcast. The overcast cleared around midnight where a small front probably passed the camp with the wind turning from SSE to SSW and the wind speed increasing to 15 kn for 3 hours.  Temperature between -22 to -8°C. Wind 5-10 kn from SSE the rest of the day.

Ice from the Last Glacial Maximum
The CFA lab closed today – and promise that they will open again next year. 620 m of ice was processed this year – 1930 m of ice more to process during the two next years. GOOD JOB!

FL, Dorthe Dahl-Jensen

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