Daily reports from the NGRIP-camp - week 27 year 2001
Monday, July 2nd
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| Daily life |
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| Science |
| Shortly after midnight Monday morning the drill got stuck. Unlike the
previous years the sticking of the drill did, however, not come as a big
surprise. Due to the high temperature of the ice close to the bottom, the
ice chips produced by the knives are not brittle, but more like a mush
that tends to pack around the drill head during drilling. Fortunately this
year the drillers knew how to handle the situation because of the experience
from last year. The ice packed around the drill head can be melted with
pure glycol. Last year it was realized that it is not necessary with large
amounts of glycol to free the drill, the important thing is that the glycol
reaches the drill and the bottom of the hole. It is also important that
action is taken quite fast, otherwise ice chips, which are present in the
drill liquid, will start piling up on top of the drill and thereby making
access difficult. If glycol is simply poured into the hole at the top,
the glycol will eventually sink to the bottom due to its high density,
but at that point most of the glycol will already be saturated with water
due to melting of ice from the sides of the hole and melting of ice chips
in the hole. Therefore the glycol will not be very efficient in melting
ice at the bottom. This problem is avoided by dropping glycol into the
hole in solid form. At the surface small glycol pills are produced in a
cold freezing unit. Those pills are dropped into the hole where they sink
to the bottom in a couple of hours. At the bottom the temperature is higher
than at surface and the pills dissolve and start attacking the troublesome
ice. At two o?clock in the night 5 kg of such glycol pills were put in
the hole and at seven in the morning the tension in the cable started to
release... and the drill was free again! |
| Logistics |
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Tuesday, July 3rd
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| Daily life |
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| Science |
| The drilling restarts after the eventful day yesterday. Because of
the glycol that was dropped in the hole there is now quite some slush at
the bottom, but nevertheless the drilling is reasonable, and more than
2 m of core is retrieved. The depth at the end of the day is 2986 m. According
to estimates based on radar reflections the thickness of the ice at NGRIP
is between 3050 m and 3100 m. With the present speed of drilling there
is thus still some way to go. |
| Logistics |
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Wednesday, July 4th
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| Daily life |
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| Science |
| Den glykol som blev hældt i borehullet for at frigøre
boret, kommer med op med isspånerne og borevæsken ved hver
boring. Nede i bunden af hullet hvor der er varmt er glykolen flydende,
men når den trækkes med boret op gennem den langt koldere is
højere oppe i iskappen fryser den inde i boret. Det medfører
at når boret når overfladen er det helt pakket med frossen
glykol og isspåner, som man bliver nødt til at smelte førend
boret kan renses og iskernen kan komme ud/fri. Det kræver stor forsigtighed
og tålmodighed at opvarme boret for at smelte glykolen uden at iskernen
tager skade, men det er muligt. Man har også eksperimenteret med
at smøre den nederste del af kernetruget med voks inden boringen,
så kernen bliver lettere at frigøre når den kommer op.
Det ser ud til at hjælpe selvom det selvfølgelig ikke løser
problemet med den frosne glykol. |
| Logistics |
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Thursday, July 5th
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| Daily life |
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| Science |
| The glycol that was put in the hole to free the drill comes up with
the chips and the drill liquid in the drill after each run. Down at the
bottom of the hole where it is warm the glykol is liquid, but during the
pull up of the drill through the much colder ice higher up in the ice sheet
the glycol refreezes inside the drill. This implies that when the drill
reaches surface it is completely packed with frozen glycol and chips, which
has to melted before the drill can be cleaned and the ice core can be recovered.
It takes great patience and caution to heat the drill and melt the glycol
without damaging the ice core, but it is possible. Today it was tested
to wax the lower part of the inner core barrel before drilling in order
to ease freeing the core af. It seems to help. |
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Friday, July 6th
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| Daily life |
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| Science |
| 2.17 m of ice core are obtained in 6 runs and 8.25 m of previously
drilled core are processed in the science trench. The electrical properties
of the ice are measured, but it is not possible to determine if the transition
to the previous interglacial period - the Eemian - has been passed. A thin
section of the ice is produced. A thin section is an about 0.5 mm thin
slice of ice that is prepared with a very sharp knife. The thin section
is fixed on a glass plate and when the plate is placed between two crossed
polarizers it is possible to distinguish the individual crystals in the
sample. That is, the crystals show different colors depending on their
orientation in the sample. The size of the crystals depends on the amount
of soluble and insoluble impurities in the ice and of the temperature of
the ice. In the GRIP ice core the size of the ice crystals in the glacial
ice, which is characterized by a high concentration of impurities, is of
the order of millimeters, while the crystals are several centimeters in
diameter during the Eemian, which has a very low concentration of impurities.
The crystals in today?s NGRIP
thin section are more than 6 cm in diameter. At first this indicates that
the Eemian ice has been reached. However, it has to be taken into account
that the crystal size also depends strongly on the temperature of the ice,
such that the crystals are growing faster the warmer it is. At the bottom
of the GRIP hole the temperature is about -10 C, while in the NGRIP hole
it is now close to -5 C. The large crystals are therefore partly due to
the high temperature of the ice. The reaching of the Eemian will be approved
by reaching ?event 1?, a characteristic very short (<100 yrs) cold period
that appeared just before termination of the Eemian. |
| Logistics |
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Saturday, July 7th
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| Daily life |
The wind speed is up to 23 m/s, so the planned BBQ is canceled.
Tonight?s program is therefore as follows:
Drink in the Techno-work-shop.
Lobsters followed by Japanese curry soup.
Warm chocolate with Rum and Cream.
Dance until it gets dark... |
| Science |
| Eight runs result in 2.55 m of ice core. The final depth is 2994 m. |
| Logistics |
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Sunday, July 8th
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| Daily life |
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| Science |
| The drill got stuck again. In the morning the hole was filtered, and
after the first drilling it was not possible to pull up the drill. The
pull in the cable was gradually increased, but the only result of that
was that the electronic brake broke, and the cable started to spool down
freely into hole. The manual brake was also overloaded and had to be repaired
before the cable can be pulled up and glycol can be dumped in the hole.
It doesn?t look too good. |
| Logistics |
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Continue to Week 28
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