Jökull - 01.12.1969, Side 43

20° 15° 10° 15° 10° 15° 10° 6°
Fig. 7. The location of the 0° C isotherm at
50 m depth northeast of Iceland in June 1952—
1960. ('Stefánsson 1962, p. 206). The tempera-
ture in the shaded area is below 0° C.
south of Iceland on the other was close to 8° C
in June 1968.
Fig. 9 shows the extension of the polar front
east of Iceland as measured by an airborne in-
frared radiation thermometer in April 1968
(Pickett and Alhey 1968). These are the most
detailed measurements of the front in this
region to this clate since they were made con-
tinuously and in one day.
As pointed out by the author (Malmberg
1967 a), the extension of the polar front has
thrown light on the well-known eastward shift
in the herring migration in North and F.ast
Icelandic waters (Jakobsson and Vilhjálmsson
1967, Jakobsson 1969).
DISCUSSION
The causes of the changes in the hydro-
graphic conditions northeast of Iceland in the
last few years are more or less unknown, but
here it will be attempted to point out possible
explanations. In general, sea-air interaction is
a well-known feature. Studies of the various
conditions in the atmosphere are often used
Fig. 6 shows the temperature ancl salinity
profiles of the section Langanes NE — fan
Mayen in June 1957, 1965 and 1968. The
changes which have taken place in this region
during the last few years are especially
clear when these profiles are compared, e.g.
June 1957, which represents a normal vear of
the 1950—1958 period, and June 1965 and 1968
which belong to the later period. The distri-
bution of the 0° C isotherm at 50 m north-
east of Iceland shown in Figs. 7 and 8 is also
a clear indication of these changes. The condi-
tions in June 1968 were quite exceptional.
since the cold tongue usually founcl deep off
the coast — even in the very colcl years 1965
and 1967 — in June 1968 covered a long
stretch of the coast from Skjálfandi in the
north to Reyðarfjörður in the east. The polar
front in the waters east of Iceland has thus
advanced and in 1968 it reached the Icelandic
c°ast and expanded farther eastwards in the
Norwegian Sea than previously observed.
Furthernrore, it should be noted that the
temperature difference in the waters north and
east of Iceland on one hand and west and
Fig. 8. The location of the 0° C isotherm at
50 m depth northeast of Iceland in June 1961—
1968. The temperature in the shaded area is
below 0° C.
JÖKULL 19. ÁR 39