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Sea ice monitoring of Icelandic waters as well as archiving of sea
ice observation data is looked after by the Icelandic Meteorological
Office. Icelandic waters are defined as the economic zone around Iceland,
extending outwards to a 200-nautical miles distance from the coast or
to the midline between Iceland and Greenland in the Denmark Strait.
Sea ice movement
Annual extension of sea ice in the vicinity of Iceland fluctuates between
open sea across the Denmark Strait in late summer to sea ice in the
Strait in late winter covering the ocean at the coast of East Greenland
halfway towards Iceland. Much of the sea ice is carried by the East
Greenland Current from the Arctic Ocean and the Northern Greenland Sea
but considerable amounts form during winter along the coasts of Greenland
further south. Besides variable amounts being brought south by the East
Greenland Current, year-to-year fluctuations in surface ocean conditions
in the Denmark Strait and the Iceland Sea give rise to different sea
ice extent in Icelandic waters. However, the final cause at present
resulting in sea ice reaching as far east as sailing routes around northwest
and north Iceland, and even to the coasts, is the effect of prevailing
winds, that is, the atmospheric pressure configuration over the North
Atlantic. In earlier centuries of colder climate, with more extensive
sea ice in the Greenland Sea, Icelandic coasts were visited by sea ice
Sea ice in the Denmark Strait (Greenland Sound)
The charts shown below are based on sea ice reconnaissance flights
of the Icelandic Coast Guard and supplemented by ship reports and other
1 displays a rather normal extent of sea ice in the Denmark Strait in
June, soon after maximum extent in late May. The chart resulted from
an expedition in June 1982 on board the Soviet icebreaker Otto Schmidt
with Icelandic participation. Meteorological and oceanographic observations
were made in the marginal sea ice zone between Iceland and Greenland.
The broken line in Figure 1 displays the general position of the sea
ice edge during the expedition. The encircled points show the locations
of oceanographic stations. During middle of June - the month of the
cruise - the sea ice is normally on retreat but still extensive.
Figure 2 shows in detail the characteristics of part of the sea ice
edge investigated during the cruise, described by the international
sea ice symbols, at that time newly adopted. The sea ice amount was
still quite large after the gradual accumulation through the winter
months. The sea ice in the southern part of the area investigated was
in general characterised by thick ice. However, the overall panorama
during the cruise was surprisingly variable in terms of concentration,
stage of development, floe size and other ice features.
3 indicates position changes of the ice edge in the Denmark Strait in
June, 1982. The eastward movement of the ice edge was associated with
moderate winds from south, southwest and west.
Examples of sea ice incidents
Sea ice off the Icelandic coasts has been recorded for centuries, first
by remarks in annals and diaries kept by farmers and officials, and
in a more regular manner during the last couple of centuries. In an
effort to find a measure of variability from one year to another, an
index was developed indicating the severity of sea ice incident during
a particular year along the coasts of Iceland. The index refers both
to the extent of the Icelandic coastline being visited by sea ice and
number of weeks with recorded sea ice during the year.
4 shows the sea ice index during most of 20th century. During the first
two decades heavy sea ice was quite common along the coasts of Iceland,
but in the 1920s a drastic change occurred. Sea ice along the coasts
of Iceland became an uncommon characteristic and almost a forgotten
phenomena around the middle of the century. An abrupt change occurred
in the mid-1960s.
5 shows the distribution of sea ice along the northern coast of Iceland
in February 1965. Heavy sea ice distribution occurred almost each year
following, but since 1980 widespread and long-lasting sea ice off Iceland
took place at rather irregular intervals.
6 displays a mid-summer sea ice distribution in 1984, showing the effect
of prevailing southwesterly and westerly winds due to a dominating blocking
high-pressure area over the North Atlantic.
in Figure 7 a more recent mid-winter incident in March 1988 is shown,
demonstrating a combined effect of above-average sea ice extent in the
Greenland Sea in the weeks before and atmospheric pressure configuration
favouring westerly winds.
The sea ice index graph during this century is an indication of interesting
climate changes on decadal time scales. However, changes of sea ice
distribution in Icelandic waters on smaller time scales, down to a few
days, and even from one hour to another, are important as sea ice affects
human activities on fishery grounds, sailing routes and in the most
serious scenarios can threaten access to harbours in northern Iceland.
Due to its irregular, almost erratic, behaviour, sea ice around Iceland
is an important natural feature that has to be watched and studied.
Scientific projects and integrated monitoring systems
In addition to conventional sea ice service based on flow of data from
ships and aircraft and archiving of obtained information, the Icelandic
Meteorological Office has participated in European and Nordic research
projects in the North Atlantic where international co-operation results
in increased knowledge of the physical processes involved in variable
sea ice amount on many scales. The Greenland Sea Project (GSP) and the
European Sub-polar Ocean Programmes (ESOP-1 and ESOP-2) have contributed
to improved understanding of the northern seas and a series of Nordic
research projects for the sub-Arctic have concentrated on analysis of
meteorological and oceanographic observation time series around the
North Atlantic. Useful experience in the fields of remote sensing, sea
ice modelling and so on has been gained.
More on the practical operational side, a three-year European project
in the field of information society technology was completed recently,
called 'Integrated weather, sea ice and ocean service system' (IWICOS).
Six institutions and a private company in the Nordic countries worked
together on the design of a co-operating platform of marine services
in the North Atlantic and along the Northern Sea Route in the Arctic
Ocean. Closer co-operation between different organisations will improve
service and safety at sea.
Despite indications of decreasing sea ice amount in the Arctic, the
East Greenland Current - the main current leaving the Arctic - will
continue to bring sea ice long distances south along the coasts of Greenland.
Conditions for local sea ice formation en route will also persist. Helped
by atmospheric variability, sea ice in Icelandic waters will still in
the years to come be of concern to seafarers, be they on board small
sailing boats, fishing boats, big tank ships or cruise liners.
© Thor Edward Jakobsson 2003. Dr Jakobsson is Project Manager,
Sea ice Research Unit at the Icelandic Meteorological Office in Reykjavik,