accumulation and often also by the seaward ex-
11. SKY AND AIR INDICATIONS
tension of land glaciers. Limited areas may be
11.1 Water sky: Dark streaks on the underside of low
aground. The seaward edge is termed an ice front
clouds, indicating the presence of water features
(q.v.).
in the vicinity of sea ice.
10.3.1 ICE FRONT: The vertical cliff forming the sea-
ward face of an ice shelf or other floating gla-
11.2 Ice blink: A whitish glare on low clouds above
cier varying in height from 250 m or more
an accumulation of distant ice.
above sea-level (cf. ice wall).
11.3 Frost smoke: Fog-like clouds due to contact of
10.4 Calved ice of land origin
cold air with relatively warm water, which can
appear over openings in the ice, or leeward of
10.4.1 CALVING: The breaking away of a mass of ice
the ice edge, and which may persist while ice is
from an ice wall, ice front or iceberg.
forming.
10.4.2 ICEBERG: A massive piece of ice of greatly vary-
ing shape, more than 5 m above sea-level,
12. TERMS RELATING TO SURFACE SHIPPING
which has broken away from a glacier, and
which may be afloat or aground. Icebergs may
12.1 Beset: Situation of a vessel surrounded by ice
be described as tabular, dome-shaped, slop-
and unable to move.
ing, pinnacled, weathered or glacier bergs.
12.2 Ice-bound: A harbour, inlet, etc. is said to be
10.4.2.1 Glacier berg: An irregularly shaped iceberg.
ice-bound when navigation by ships is prevented
on account of ice, except possibly with the as-
10.4.2.2 Tabular berg: A flat-topped iceberg. Most
sistance of an icebreaker.
tabular bergs form by calving from an ice
shelf and show horizontal banding (cf. ice
12.3 Nip: Ice is said to nip when it forcibly presses
island).
against a ship. A vessel so caught, though un-
damaged, is said to have been nipped.
10.4.2.3 Iceberg tongue: A major accumulation of
icebergs projecting from the coast, held in
12.4 Ice under pressure: Ice in which deformation
place by grounding and joined together by
processes are actively occurring and hence a
fast ice.
potential impediment or danger to shipping.
10.4.3 ICE ISLAND: A large piece of floating ice, about
12.5 Difficult area: A general qualitative expression
5 m above sea-level, which has broken away
to indicate, in a relative manner, that the sever-
from an Arctic ice shelf, having a thickness of
ity of ice conditions prevailing in an area is such
3050 m and an area of from a few thousand
that navigation in it is difficult.
square metres to 500 sq. km or more, and usu-
ally characterized by a regularly undulating
12.6 Easy area: A general qualitative expression to
surface which gives it a ribbed appearance
indicate, in a relative manner, that ice conditions
from the air.
prevailing in an area are such that navigation in
it is not difficult.
10.4.4 BERGY BIT: A large piece of floating glacier ice,
generally showing less than 5 m above sea-
12.7 Iceport: An embayment in an ice front, often of
level but more than 1 m and normally about
a temporary nature, where ships can moor along-
100300 sq. m in area.
side and unload directly onto the ice shelf.
10.4.5 GROWLER: Smaller piece of ice than a bergy bit
or floeberg, often transparent but appearing
13. TERMS RELATING TO SUBMARINE NAVI-
green or almost black in colour, extending less
GATION
than 1 m above the sea surface and normally
occupying an area of about 20 sq. m.
13.1 Ice canopy: Pack ice from the point of view of
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