27 June 2010

On the nightshift

The experimental setup of the Continuous Flow Analysis (CFA) is highly advanced
The CFA team on the night shift.

At night, while most of NEEM camp is fast asleep, there is full activity in the heated hut for Continuous Flow Analysis (CFA) in the science trench. Anna, Gideon and Paul start their night shift at 8pm, they have ‘lunch break' at 2am in the night and continue working until 8am in the morning, when it is time for Daiana, Liz and Nerilie to take over for the dayshift.

The work consists in preparing 1.1 m long sticks of ice core that are slowly melted on a melt head and analyzed for a large number of constituents. The experimental setup is highly advanced and probably one of the most complex analytical instruments ever put on an ice sheet. The analysis involves separation of the air from the melt water stream, splitting of the water stream in to more than 10 different channels, wet chemistry involving more than 35 chemical reagents and standards, laser scattering, absorption spectroscopy, fluorescence detection, gas chromatography and fast ion chromatography.

The result of the analysis are among others continuous high-resolution records of insoluble dust, black carbon, ionic concentrations of sodium, calcium, ammonium, sulphate and nitrate as well as discrete analysis of methane gas concentrations. Along with this, discrete samples are taken for a number of other impurity studies not analyzed in the field. Furthermore, continuous streams of water and gas from air bubbles are lead to an adjacent hut where they are analysed for among others water isotopic composition and gas concentrations, but that's a different story.

In between measurements, there is a protocol for standard calibrations and maintenance that occupies the crew for about 30% percent of the working hours. The production of one nights work is typically 10 m of ice. In this perspective, a 2.5 km ice core is rather long.

What we have done today:
1. Drilling and core logging Eemian ice. Driller's depth: 2254.36 m. Logger's depth:
    2272.60 m.
2. Processed deep ice cores to depth 2214.85 m.
3. CFA calibration and maintenance.
4. Preparing skiway for flight mission scheduled for Tuesday.

Weather: Clear blue sky during daytime; at midnight a front came in with complete cloud cover and winds up to 15 knots from SE. Temp. -15 °C to -6 °C.

Ad 1: Report from yesterday: We drilled more ice cores today. We tried a configuration with the closed hallow shaft that placed the rings 4.5 meters apart so it somewhat imitated NGRIP. The lowest ring was 18 cm above the pump, the other 4.5 m above that. So far, so good. We did three nice runs over 3.4 meters at 2.6 to 2.9 mm pitch with good chip recovery on the short Saturday.

And on Sunday the good drilling continued. We had four runs with about 3.4 meters or more and a final one that was shorter (1.65 m) due to a disengaged pump. All runs were done with the closed hallow shaft with the 4.5 meter spacing between centering rings. It appears we have again found a more or less stable mode for the moment. The drill teams will enjoy one more day together on Monday before the expected crew change on Tuesday.

FL, Anders Svensson


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