Jökull - 01.12.1969, Page 74

And, although it is not known to what an
extent ocean currents may have effected the
drift of the ice in the case above of Jan. 1952,
one is led to believe that in some cases scatter-
ed floes can drift with as much or even greater
speecl than 4% of the wind velocity.
ICE AND WINDS
EAST OF GREENLAND
Before considering the ice condition in the
year 1965, some analyses of the average condi-
tion of winds and ice north of Iceland is
necessary, because the ice that comes to the
northeast coast of Iceland must originate there.
The winds have been divided into two com-
ponents, one along the ice edge, the other
perpendicular to it, or rather to lines selected
close to its average position; Fig. 1. The ice
edge is divided into three regions, each 300
miles in length, named region N, region M
ancl region S. Monthly component values are
found from the charts of the German Weather
Office in Hamburg: Die Witterung in Uber-
see.
The position of the ice edge is taken from
the montlily ice charts issued by the British
Weather Office since March 1962. Fig. 2 shows
the position of the ice edge in relation to the
Fig. 1. The regions or lines from which the
ice limit is measured and the wind components
worked.
lines N, M ánd S. Each ice year is considered
to begin in October and end with September,
since then the ice is at its minimum as clearly
appears in Fig. 4. It is obvious that the ice
coverage is greatest in all the three regions
at the end of February, but it decreases rapid-
ly in March and April in regions N and M,
whereas the decrease is much slower in region
S between Jan Mayen ancl Iceland.
In order to get an oversight over the ice
amount each year with respect to other years
and to the average condition a graph has been
made showing the position of the ice edge
with respect to the monthly mean, Fig. 3. In
region S the ice years 1965 and 1968 stand out,
also 1967. Furthermore, there is quite apparent
ice in tliis region in the falls of 1963 and 1967.
In region M there has been an unusual
amount of ice in the fall of 1967, the following
winter and spring.
This excess of ice north of Jan Alayen in the
early winter must be to a great extent re-
sponsible for the ice at the north and east
coasts of Iceland in the spring of 1968. In
the spring of 1965 there is a maximum in
region M. This excess is due to unusually
strong westerly winds in these tracts in Febru-
ary, the same winds as prevailed in region S
and brought drift ice to the coasts of Iceland
and will be discussed later. Considering region
N, maxima appear both the winters 1955 ancl
1968; there is, however, no maximum in 1967.
In the summer of 1962 a maximum appears
also in region M. This excess lasted into the
fall, and after a 7 knots geostrophic wind com-
ponent out from the ice edge in January in
region S, ice was seen off Horn the first days
of February, 1963. But eastelv winds in this
region the following months kept the clrift
away the rest of the year.
Fig. 5 shows the average wind components
east of Greenland the years 1962 to 1967. The
most striking feature is the strong NE com-
ponent along the ice edge in winter. There
are 12 to 14 knots maxima in March and
December but minima 0 to 2 knots in June.
February reflects the exceptionally strong
westerly winds in this month in 1965. The
mean velocity in winter is 11 knots. One per
cent of this, amounting closely to the Zubov’s
formula of ice drift, is some 2i/2 rniles a clay
70 JÖKULL 19. ÁR