29 June 2010

How old is the ice?

A falcon passed by for a visit
A very rare visitor came to NEEM today - a falcon.

Due to very high temperatures up to -1.5 °C in the morning we had to cancel today's flight. There will be a new attempt tomorrow.

Today the NEEM drilling passed 2300m depth and everyone is very excited to know how old the deep ice is. Already the freshly drilled core gives a hint about in which climate the snow was deposited. In cold climates, such as a glacial period, the ice contains high concentrations of dust and other impurities which are often seen in the ice as ‘cloudy bands'. The freshly drilled ice is completely transparent, indicating that we are now drilling the Eemian interglacial ice.
Another climate proxy is the ice crystal size, which is related to both the impurity content and the temperature history of the ice. In the ice drilled over the last days we've occasionally seen ice crystals that are several cm across, which is also indicating that we are drilling in warm low-impurity ice.
The next climate indicator we get from the DEP and ECM measurements, which are measures of the dielectric properties and the conductivity of the ice, respectively. Comparison of those profiles to the corresponding profiles from the NGRIP ice core shows that we are now in the Eemian.
Probably the most robust climate indicator we get from the water isotopic composition of the ice which is measured in camp some days after the core is drilled.

We're now watching out for changes in those indicators to see if we'll reach Termination II or the onset of the Eemian which is estimated from marine cores and Chinese stalagmites to have an age of about 129,000 before present.

What we have done today:
1. Drilling and core logging Eemian ice. Driller's depth: 2282.25 m. Logger's depth:
    2301.79 m.
2. Processed deep ice cores. 11.0 m. Final depth 2253.35 m.
3. CFA measurements. 22.0 m. Final depth: 1878.25 m.
4. Adjusted weather station wind direction indicator.
5. Grooming skiway.

Ad. 4: The direction of Davis weather station anemometer was checked by compass and found to be slightly offset. The direction was adjusted by approx. 15 deg. to make the anemometer point true north. It is now fixed in that direction.

Weather: Overcast with light snow showers in the morning, but clearing up during the day and clear blue sky at night. In the morning absolutely no wind and temperatures up to -1.5 °C. In the evening, wind is 9 kt from ESE and temperature is -13 °C.

FL, Anders Svensson


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