Jökull - 01.12.2007, Síða 74

Thorsteinsson et al.
measured and samples for a geochemical study ob-
tained (Ágústsdóttir and Brantley, 1994). In 2002, the
lake was sampled for microbiological investigations
for the first time, with positive results (Gaidos et al.,
2004) but with the exception of heating the drilling
fluid to high temperature, these projects did not in-
corporate the techniques intended to decontaminate
the drilling water described here. The development
of methods for drilling and sampling that minimize
the probability of contamination is of particular inter-
est for future exploration of the physical, geochemical
and biological properties of Antarctic subglacial lakes
(Fard, 2002; Priscu and Christner, 2004; Siegert et al.,
2001). Close to 150 subglacial lakes are now known
to exist beneath the Antarctic Ice Sheet (Siegert et al.,
2005), but none of them have yet been directly sam-
pled due to their remote locations, the technical chal-
lenge of penetrating 1–4 km of ice in a polar envi-
ronment, and concerns about contamination from the
surface.
A HOT WATER DRILLING SYSTEM
THAT INCORPORATES IN-LINE
STERILIZATION
A hot water drilling system has been designed and
built at the Hydrological Service Division of the Na-
tional Energy Authority (Orkustofnun), Iceland. The
main components of this system are shown in Figure
1 and specified further in Table 1. Photos of individ-
ual parts and field operations are shown in Figure 2.
Snow is melted in a 600 l plastic tube in which a heat
exchanger is placed. Glycol is heated in a combustion
unit (diesel burner) and circulated in a closed loop
system between the burner and the heat exchanger.
The closed loop system is fitted with an expansion
chamber and has a total length of 35 m. The melt-
water is pumped from the plastic tub through twin fil-
ters (pore size: 50 µm) to remove large particulates
and then through a UV sterilization unit before en-
tering the combined high pressure pump and heater
Figure 1. Schematic diagram of the hot water drilling system. See Table 1 for specific information on the
individual parts. – Skýringarmynd af bræðslubornum. Einstakir hlutar borkerfis eru tíundaðir í töflu 1.
72 JÖKULL No. 57