Fróðskaparrit - 01.01.1993, Page 148

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MEASUREMENTS OF SEA BOTTOM TEMPERATURES
Jute-threads
Tarred hemp
insulation Twisted
iron wires
Fig. 1. Construction of the originally deployed cables.
have to be addressed. One involves the
measurement procedure itself and prob-
lems associated with cable breaks and
physical changes of the cables. The second
kind of difficulties involves the interpreta-
tion of the measurements. Neither of the ca-
bles was surrounded by only one water
mass. On the contrary, water from widely
different origins affected both cables. Thus
it is not a straightforward task to interpret a
variation in average bottom temperature
along one of the cable tracks.
In this publication only the first kind of
difficulty is dealt with. This is primarily a
data report presenting the results and docu-
menting the methods used in obtaining
them. In a separate paper (Hansen et al.,
1994) these results are compared to other
sources of information and interpreted.
The cables
Both cables were of the same construction
with a central copper core and a surround-
ing screen which was isolated from the core
and from the surrounding seawater (Fig. 1).
The cable construction did not change
much during the period although some of
the later cables had an extra layer of pro-
tecting canvas tape surrounded by a brass
layer to protect the cable from biological
activity.
The cable tracks are shown in Fig. 2 to-
gether with the bottom topography. These
tracks were not changed appreciably
through the period except for the landing in
Tórshavn. From the beginning in 1906 un-
til August 8th 1949 the cables were led
ashore in a small bay “Sandagerði” close
by the town. After this time the cables came
ashore at “Hvítanes”, a few miles distant
from the original point.
At the original deployment the Iceland-
cable had a total length of 318.42 n.m.
(nautical miles) while the Shetland-cable
had a length of 215.18 n.m. After each ca-
ble break the cable was spliced which may
involve a change in cable length. An origi-
nally taut cable would after splicing be
lengthened by an amount which is about