Jökull - 01.12.1969, Síða 44

Fig. 9. The polar front in the sea east of Ice-
land on April 9, 1968 surveyed by means of
an airborne radiation thermometer. (Pickett
and Athey, 1968).
for comparison with conditions in the sea in
order to understand better the acting forces
involved. Various atmospheric observations are
also more copious than those of the sea and
thus more valuable for statistical studies. Many
scientists have thus pointed out similar trends
in the physical properties of the atmosphere
and the sea in various regions. Stefánsson
(1962, p. 209) has thus shown a correlation be-
tween wind conditions north of Iceland and
hydrographic conditions deep off Langanes
during the years 1950—1958. In this special
study the effect of the atmospheric circulation
may be indirect rather than direct (Stefánsson
and Gudmundsson 1969). The recent changes
in the East-Icelandic Current are probably due
to more distant air and sea conditions than
those of the Iceland Sea itself. Various scient-
ists have shown a large-scale sea-air interaction
in the North-Atlantic south of Iceland (a. o.
Namias 1965, Rodewald 1967, 1968, Lee, Cor-
crum. and Levastu 1967, Dickson and Lee
1969). Rodewalds results agree fairly well with
the findings here presented. As shown in Fig.
10 Rodewald obtaines a low correlation coefli-
cient between the pressure anomalies in late
winter of the periods 1956—1960 and 1961 —
1965 in the area east of Iceland, whereas the
correlation coefficient over the entire North
Atlantic is high.
40 JÖKULL 19. ÁR
Björnsson (1969) discusses possible explana-
tion of the ice drift north of Iceland.
Sea ice no doubt affects the liydrographic
conditions, as well as being partly dependent
on these same conditions. There is also a fair
agreement between the recent changes in the
hydrographic conditions northeast of Icelancl
and the ice conditions in the area and at the
coasts of Iceland. According to Strúbing (1968)
there is a close correlation between air pres-
sure over the North Polar Sea and ice quantity
in the East-Greenland Current a few months
later. Part of the East-Icelandic Current is, on
the other hand, a branch of the East-Green-
land Current or rather the waters of its east-
ern boundaries (Stefánsson 1962, p. 57). The
East-Icelandic Current and the drift ice it con-
tains may thus also be affected by conditions
in the North Polar Sea. The sea ice, respond-
ing to weather, wind conditions and ocean
currents, affects the water masses by cooling
them and decreasing their salinity. The de-
crease in salinity leads to a lowering in the
density of the surface layers, which in turn
increases the vertical stability. The cooling
effect of cold winds the following winter, and
of course sea ice, then only reaches the sur-
face layer; the cooling cannot break down the
stability and the surface layer cools down more
and earlier than otherwise.
Fig. 10. Correlation between the March-pres-
sure anomalies of the periods 1956—1960 ancl
1961—1965. (Rodewald 1967).