7. OPENINGS IN THE ICE
7.4.1 SHORE POLYNYA: A polynya between pack ice and
the coast or between pack ice and an ice front.
7.1 Fracture: Any break or rupture through very
7.4.2 FLAW POLYNYA: A polynya between pack ice and
close pack ice, compact pack ice, consolidated
fast ice.
pack ice, fast ice, or a single floe resulting from
deformation processes. Fractures may contain
7.4.3 RECURRING POLYNYA: A polynya which recurs in
brash ice and/or be covered with nilas and/or
the same position every year.
young ice. Length may vary from a few metres
to many kilometres.
8. ICE-SURFACE FEATURES
7.1.1.1 Tide crack: Crack at the line of junction be-
8.1 Level ice: Sea ice which is unaffected by defor-
tween an immovable ice foot or ice wall and
mation.
fast ice, the latter subject to rise and fall of
8.2 Deformed ice: A general term for ice that has been
the tide.
squeezed together and in places forced upwards
7.1.1.2 Flaw: A narrow separation zone between
(and downwards). Subdivisions are rafted ice,
pack ice and fast ice, where the pieces of ice
ridged ice and hummocked ice.
are in chaotic state; it forms when pack ice
8.2.1 RAFTED ICE: Type of deformed ice formed by one
shears under the effect of a strong wind or
piece of ice overriding another (cf. finger raft-
current along the fast ice boundary (cf. shear-
ing).
ing).
8.2.1.1 Finger rafted ice: Type of rafted ice in which
floes thrust "fingers" alternately over and un-
der the other.
8.2.2 RIDGE: A line or wall of broken ice forced up by
pressure. May be fresh or weathered. The sub-
merged volume of broken ice under a ridge,
forced downwards by pressure, is termed an ice
7.2 Fracture zone: An area that has a great number
keel.
of fractures.
8.2.2.1 New ridge: Ridge newly formed with sharp
peaks and slope of sides usually 40. Frag-
7.3 Lead: Any fracture or passage-way through sea
ice which is navigable by surface vessels.
ments are visible from the air at low altitude.
7.3.1 SHORE LEAD: A lead between pack ice and the
8.2.2.2 Weathered ridge: Ridge with peaks slightly
rounded and slope of sides usually 30 to 40.
shore or between pack ice and an ice front.
Individual fragments are not discernible.
7.3.2 FLAW LEAD: A passage-way between pack ice
and fast ice which is navigable by surface ves-
8.2.2.3 Very weathered ridge: Ridge with tops very
rounded, slope of sides usually 2030.
sels.
7.4 Polynya: Any non-linear shaped opening en-
8.2.2.4 Aged ridge: Ridge which has undergone con-
closed in ice. Polynyas may contain brash ice
siderable weathering. These ridges are best
and/or be covered with new ice, nilas or young
described as undulations.
ice; submariners refer to these as skylights.
Sometimes the polynya is limited on one side
8.2.2.5 Consolidated ridge: A ridge in which the base
by the coast and is called a shore polynya or by
has frozen together.
fast ice and is called a flaw polynya. If it recurs
in the same position every year, it is called a
8.2.2.6 Ridged ice: Ice piled haphazardly one piece
recurring polynya.
over another in the form of ridges or walls.
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