Jökull - 01.12.1972, Page 12

After this account of the history of sea ice
observations a short survey of the results of the
ice observations will be given.
Fig. 1 shows the sea ice distribution to the
end of the year 1971. The presentation is the
same as that used by Koch (1945), and the first
part of the figure, until 1939, is copied from
his book “The East Greenland Sea” with the
exception that sorne ice is added on to the
figure in outline, according to later informa-
tion. For the year 1918, use was made of an
unpublished diary written by Matthias Eggerts-
son, a minister at Grímsey at that time. No
account is taken of observations of single floes
and ice which was farther from the coast than
20 nautical miles. This was done in order to
avoid an increase of sea ice reports in the last
decades as compared with earlier ones, merely
because fishing vessels now go much farther
out to sea than they did before. Reports of
icebergs, which may drift away frorn the main
ice are also omitted, except when they were
surrounded by an area of drift ice.
Fig. 2—7 show the distribution of the sea
ice from one month to another. The figures
are continuation of similar figures presented by
Koch (1945) and show where sea ice lias been
observed in a particular month. No attempt is
made to indicate the density of the ice, but
reports of single floes were omitted, and areas
of slush and young ice are indicated by hatch-
ing. Charts marked with an asterisk indicate
that no reports of sea ice were received at the
Icelandic Meteorological Office in that parti-
cular month, but empty charts indicate a total
lack of ice within the chart area, according to
observations. The base map is clrawn in a
Mercator projection! limited by the latitude
circles of 62.5 and 68° N, and the longitude
circles of 10° and 27° W.
When these charts are compared with one
another, the variability of the ice in the Den-
mark Strait becomes very evident. It is also
clear, that srnall differences in the extent of
the ice may cause great variations in its effects.
To mention some examples, sea ice was not ob-
served by coastal vessels in April and May
1959, even though it was rather extensive, and
not very far from the Icelandic shores. The sea
ice caused only minor troubles to shipping in
March and April in 1944 and 1967, even though
10 JÖKULL 22. ÁR
its extent in those cases was only slightly less
than in the year 1965, when it hacl very serious
effects on navigation.
It is not claimed that tliese figures can be
used to explain the movements of the sea ice,
since each one covers a small area, but a rather
long time. They are intendecl to give a general
survey of the ice conditions and to indicate
from what time intervals collection of more ob-
servational material might be attempted in
order to obtain a more complete picture of the
historical ice conditions.
ACKNOWLEDGEMENT
The material for the charts of 1970 and 1971
has been coilected a.,nd analysed by Mr. Eiríkur
Sigurðsson.
REFERENCES
Det Danske Meteorologiske Institut, Charlott-
enlund: Isforholdene i de Arktiske Have
1913 og 1949-1956.
— Isforholdene ved Grönland 1957—1962.
Eggertsson, Matthias: Unpublished Diary.
Grímsey, N.-Icelancl.
Eytliorsson, Jón. 1953—1966: “Report on Sea
Ice off the Icelandic Coasts”, yearly reports
from Jan. 1953 to Sept. 1966. Jökull 1953—
1966.
Eythorsson, /.J a?id H. Sigtryggsson. 1971: The
Climate and Weather of Iceland. The Zoo-
logy of Iceland. Vol. I, Pt. 3, 62 pp. Munks-
gaard. Copenhagen and Reykjavík.
Kocli, L. 1945: The East Greenland Ice. Med-
delelser fra Grönland. Bd. 130 nr.3, Köben-
havn.
Marine Division (Met, O. 1) Meteorological
Office, Bracknell: Ice at the end of each
month. May 1962—Dec. 1968.
Oceanographic Division, U. S. Naval Oceano-
graphic Office: Report of the Arctic Ice
Observing and Forecasting Program, 1961—
1964.
— Birds Eye 1—62 to 4—67. Unpublished
Manuscript, Washington D.C.
Sigtryggsson, H. 1967: Report on Sea Ice off