APPENDIX A: SEA ICE NOMENCLATURE, ARRANGED BY SUBJECT
[Courtesy of the World Meteorological Organization (WMO 1970)]
2.2 Nilas: A thin elastic crust of ice, easily bending
1. FLOATING ICE: Any form of ice found floating
on waves and swell and under pressure, thrusting
in water. The principal kinds of floating ice are lake
in a pattern of interlocking "fingers" (finger raft-
ice, river ice, and sea ice which form by the freez-
ing). Has a matt surface and is up to 10 cm in
ing of water at the surface, and glacier ice (ice of
thickness. May be subdivided into dark nilas and
land origin) formed on land or in an ice shelf. The
light nilas.
concept includes ice that is stranded or grounded.
2.2.1 DARK NILAS: Nilas which is under 5 cm in thick-
1.1 Sea ice: Any form of ice found at sea which has
ness and is very dark in colour.
originated from the freezing of seawater.
2.2.2 LIGHT NILAS: Nilas which is more than 5 cm in
1.2 Ice of land origin: Ice formed on land or in an
thickness and rather lighter in colour than dark
ice shelf found floating in water. The concept in-
nilas.
cludes ice that is stranded or grounded.
2.2.3 ICE RIND: A brittle shiny crust of ice formed on a
1.3 Lake ice: Ice formed on a lake, regardless of ob-
quiet surface by direct freezing or from grease
served location.
ice, usually in water of low salinity. Thickness
to about 5 cm. Easily broken by wind or swell,
1.4 River ice: Ice formed on a river, regardless of
commonly breaking in rectangular pieces.
observed location.
2.3 Pancake ice: cf. 4.3.1.
2. DEVELOPMENT
2.4 Young ice: Ice in the transition stage between nilas
and first-year ice, 1030 cm in thickness. May
2.1 New ice: A general term for recently formed ice,
be subdivided into grey ice and grey-white ice.
which includes frazil ice, grease ice, slush and
shuga. These types of ice are composed of ice
2.4.1 GREY ICE: Young ice 1015 cm thick. Less elas-
crystals which are only weakly frozen together
tic than nilas and breaks on swell. Usually rafts
(if at all) and have a definite form only while they
under pressure.
are afloat.
2.4.2 GREY-WHITE ICE: Young ice 1530 cm thick. Un-
2.1.1 FRAZIL ICE: Fine spicules or plates of ice, sus-
der pressure more likely to ridge than to raft.
pended in water.
2.5 First-year ice: Sea ice of not more than one
2.1.2 GREASE ICE: A later stage of freezing than frazil
winter's growth, developing from young ice;
ice when the crystals have coagulated to form a
thickness 30 cm2 m. May be subdivided into thin
soupy layer on the surface. Grease ice reflects
first-year ice / white ice, medium first-year ice and
little light, giving the sea a matt appearance.
thick first-year ice.
2.1.3 SLUSH: Snow which is saturated and mixed with
2.5.1 THIN FIRST-YEAR ICE/WHITE ICE: First-year ice 30
water on land or ice surfaces, or as a viscous
70 cm thick.
floating mass in water after a heavy snowfall.
FIRST-YEAR ICE:
First-year ice 70120
2.5.2 MEDIUM
2.1.4 SHUGA: An accumulation of spongy white ice
cm thick.
lumps, a few centimetres across; they are formed
from grease ice or slush and sometimes from
2.5.3 THICK FIRST-YEAR ICE: First-year ice over 120 cm
anchor ice rising to the surface.
thick.
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