Jökull - 01.12.1969, Page 66

Sea Ice in Satellite Pictures
BORGTHÓR H. JÓNSSON,
THE ICELANDIC METEOROLOGICAL OFFICE, KEFLAVIK, ICELAND
ABSTRACT
The outflow of ice from the Polar basin
through the gap betioeen Spitsbergen and
Greenland has been investigated with. the aid
of salellite pictures and monthly surface
pressure tnaps. An attempt has been made lo
classify the types of sea iee which occur in the
coastal waters of northern Iceland. It is sug-
gested that persistent northerly toinds over the
area east of Greenland will cause greater
amount of ice to drift into that area, and con-
sequently enhance the chances that the ice-
pack will drift all the toay to the north coast
of Iceland. A suggestion is made that by using
7,ubov’s empirical rule a 10 to 15 days ice fore-
cast may be prepared, once the exact position
of the ice edge has been mapped by the aid of
satellite pictures.
Observation of sea ice conditions by weather
satellites is a new and valuable aicl in charting
ancl following the movement of the ice edge.
The purpose of this article is to show that
variations in the extent of the ice tongue, that
reaches southward between Spitsbergen and
East-Greenland, are probably caused by changes
in the circulation of the atmosphere.
The drift of the ice island Arlis II from
Point Barrow in Alaska (1961—1965) to the Den-
mark Strait seems to indicate that perhaps there
is a greater and more erratic outflow of sea
ice from the Beaufort sea into the North-Atlan-
tic than was generally believed up to present
time.
The estimate 10,000 km3 of ice, that the East-
Fig. 1. Extreme ice limits in April and May.
“The enormous year to year variations froni
the conditions defined as “average’’ cannot
be overemphasized. In this connection, parti-
cular attention is called to the series of charts,
which show the extreme limits of ice in the
North Atlantic region in the periocl 1898—
1938. “As in the case of weather data, aver-
ages cannot be used to determine the pre-
cise nature of conditions for any specific time
in the future. The average can only serve as
a record expectancy in very general terms.“
(From Iceatlas of the Northern Hemisphere.
Published by the Hydrographic Office, United
States Navy.)
62 JÖKULL. 19. ÁR