Fróðskaparrit - 01.01.1993, Síða 153

MEASUREMENTS OF SEA BOTTOM TEMPERATURES
157
have compared the cable temperatures from
the Shetland cable to temperature measure-
ments made from research vessels within
one month of the cable measurements.
They found a close relationship between
the two different methods except that the
cable data could be offset considerably for
some periods. Thus the high cable temper-
atures seen in Fig. 3 for the years 1945-47
was considered an artifact. They concluded
that the cable temperatures presented here
should not be used uncritically to evaluate
long-term trends.
The seasonal variation is less sensitive to
the errors introduced by cable breaks and
other sources and Figs. 3 and 4 indicate
long-term changes in the amplitude of the
seasonal signal which might be of climatic
interest. Especially interesting is the period
around 1910 where the cable measure-
ments indicate almost no seasonal variation
in temperature. This coincides with what is
known to be an anomalous situation (Dick-
son et al., 1984; Dickson et ai, 1988). The
interpretation of these changes, however,
requires a more detailed analysis of the in-
fluence of different water masses on the ca-
ble temperature and additional information
on the long-term variations of these water
masses. These questions are discussed by
Hansen et al. (1994).
Acknowledgement
The author gratefully acknowledges the
work by many living and non-living col-
leagues in the acquisition of the measure-
ments and the assistance of B. Hansen and
H.P. Joensen in the preparation of the man-
uscript.
References
Dickson, R.R., Malmberg, S.A., Jones, S.R. and Lee,
A.J. 1984. An investigation of the earlier great sali-
nity anomaly ofl910-14 in waters west of the British
Isles. Intemational Council for the Exploration of
the Sea, Contributions to Council Meetings
1984/GEN: 4:1-30.
Dickson, R.R., Meincke, J., Malmberg, S.A. and Lee,
A.J. 1988. The “Great Salinity Anomaly” in the
Northem North Atlantic 1968-1982. Prog. Ocea-
nog. Vol.20: 103-151.
Hansen, B., Joensen, H.P. and Michelsen, V.E. 1994.
Bottom temperatures between Iceland and Shetland
1906-1962 measured in telegraph cables. Intema-
tional Council for the Exploration ofthe Sea, Con-
tributions to Council Meetings 1994/S: 5: 1-14.
Table 1. Data from the Shetland (Tórshavn - Burwick)
cable. The table shows the calculated cable temperature
for each date when cable resistance has been succesful-
ly measured. When cable breaks have occurred between
two measurements this is indicated by updated values
for cable length and standard resistance. Resistances are
in International Ohm for the whole period.
Table 2. Data from the Iceland (Tórshavn - Seyðis-
fjørð) cable. The table shows the calculated cable tem-
perature for each date when cable resistance has been
succesfully measured. When cable breaks have occurred
between two measurements this is indicated by updated
values for cable length and standard resistance. Resis-
tances are in Intemational Ohm for the whole period.
Vagn Erik Michelsen
Varðabú 24
FR-100 Tórshavn