Jökull - 01.12.1969, Síða 76

Fig. 4. The average distance of the ice edge
from the lines N, M ancl S 1962—1968, niea-
sured in nautical miles.
belt becomes serious when northwesterly com-
ponent sets in. This happened in the year
1965. In December the average outward com-
ponent was 6 knots and again 9 knots in Febru-
ary, at the time of the year when the ice belt
is widest.
Although one can point out different cases
when the ice responds to the wind, the graphs
of the wind component normal to the ice edge
and the movements of the ice edge do not
correlate closely. The correlation coefficient of
these two factors was only 0.31 in region S and
still smaller in the other regions. All cases,
when the wind component perpendicular to
the ice edge was 3 knots geostrophic or more,
were taken separately and compared to the
movement of the ice edge. Then the correla-
tion coefficient in region N was 0.05, 0.24 in
region M and 0.44 in region S. The poor cor-
relation in the northern regions is no doubt
due to various reasons: First, the period, a
month, may be too long because of drift be-
tween regions; also the lines N, M ancl S do
not always coincide with the moving ice edge.
Secondly, the ice charts are inexact in these
northerly tracts, especially in winter. In the
third place, the main reason is probably that
the movement of the ice edge is less depen-
dent on winds in these regions than it is on
the temperature and currents of the ocean.
The correlation coefficient 0.44 in region S
is large enough to show that winds are to a
72 JÖKULL 19. ÁR
considerable degree responsible for the move-
ment of the drift ice there, although other
factors also play their roles. They are sea cur-
rents, freezing in winter and melting in spring
and sunnner. However, sudden outbreaks are
no doubt due to winds. Two times during this
period of six years the outward movement of
the edge exceeded 100 miles in a month, in
February 1965 and March 1967. In both cases
the NW wind component was decisive.
As mentioned before, there is a small cor-
relation between the movement of the ice
edge in each regiort and simultaneous wind
component alongside it. On the other hand
there is a connection between the movement
of the ice edge in region S and the difference
between the strength of the NE wind there
and in region M. The correlation coefficient
is 0.46. This fact shows that when ice drift is
greater through the northern limits of region
S than the drift through the southern limits
towards the southwest, the ice spreads out but
is not entirely pressed together. This effect
was present in 1968. Then the mean NE wind
component for the months February and
March was only 8 knots in region S compared
to 15 knots in region M. The difference, 8
knots, is sufficient to account for a drift dif-
ference of 100 miles in these two months. Since
the width of the ice belt was close to 300 miles
at this time, the outward movement of the ice
edge might have amounted to 100 miles due
to this effect from the beginning of February
to the end of Marcli.
In recent years very cold outbreaks of arctic
air south along the east coast of Greenland
have been more frequent than before. And it
is mainly due to these outbreaks that the
Fig. 5. The average wind components east of
Greenland for the years 1962—1968. Geo-
strophic wind in knots.