Author Topic: Sea Ice Types  (Read 6983 times)

Janet Jaguar

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Sea Ice Types
« on: November 07, 2012, 01:01:08 am »



Taken from FORECASTERS HANDBOOK FOR THE ARCTIC, Appendix A: Glossary and Report of the cruise of the revenue marine steamer Corwin in the Arctic Ocean in the Year 1884, supplemented with other government and Greenpeace images, and a few additional archaic ice terms.  Some sailing terms are at the end.  The resource links contain a great many more terms than are listed here.  Click on the pictures to enlarge them.  (Approximate conversions: 16 kilometers = 10 miles; 10 meters = 11 yards.)


BAY ICE:  An archaic term that covers the range from nilas to grey. This was bad for sailing ships as it could stop them entirely whereas they could force (or bore) through much heavier floes given wind and some looseness in the pack.  (Kevin Wood)

BERGY BIT:  A large piece of floating glacier ice, generally showing less than  16 ft. (5  m) above  sea  level  but  more  than  3  ft.  (1 m) and normally about 120 to 360 sq.yds. (100-300 sq.m.)  in  area. 


BRASH  ICE:  Accumulations  of floating  ice  made  up  of fragments  not more  than  6.5 ft. (2  m)  across,  the  wreckage  of other  forms  of ice.

BROKEN ICE:  Ice broken up into sharp pieces.  (from old logs and new image captions)

CAKE OF ICE:  Any random piece of ice big enough to tie a ship up to. (Kevin Wood)


FAST  ICE:  a.k.a. LAND-FLOE or LAND ICE, a.k.a. GROUND ICE; Sea  ice  that  forms  and  remains  fast  along  the  coast,  where  it  is  attached  to the  shore,  to  an  ice  wall,  to  an  ice front,  between  shoals  or  grounded  icebergs.  Vertical fluctuations may be observed during changes of sea level.  Fast ice may  be formed on site from  sea  water  or  by  freezing  of pack  ice  of any  age  to  the  shore,  and  it  may  extend  a few yards (meters)  or several  hundred miles  (kilometers)  from  the  coast.  Fast ice may be more than one year old and may then be prefixed with appropriate age category (old, second year, or multiyear).  If it is thicker than about 7 ft.  (2  m)  above sea  level,  it  is  called  an ice  shelf. 


FLOE:  Any relatively flat, isolated piece of sea ice 65 ft. (20 m) or more across.  Floes are subdivided according to horizontal extent as follows:      GIANT:  over 6 mi (10 km)      VAST:  1-6 mi (2-10 km)      BIG:  550-2200 yd.  (500-2000 m)      MEDIUM:  110-550 yd.  (100-500 m)      SMALL:  22-110 yd.  (20-100 m) 


FRAZIL ICE:  Fine spicules, or plates of ice, suspended in water.   


GRAY ICE:  Young ice 4 to 6 in (10-15 cm) thick.  Less elastic than nilas and breaks on swell.  Usually rafts under pressure. 


GREASE ICE:  A later stage of freezing than frazil ice.  It occurs when the crystals have coagulated to form a soupy layer on the surface.  Grease ice reflects little light, giving the sea a matte appearance. 

GROUND ICE: See FAST  ICE


GROWLER:  Smaller  piece of ice  than  a bergy  bit,  often transparent  but  appearing  green or  almost  black  in  color.  Usually extends less than 3 ft.  (1 m) above  the  sea  surface  and normally  occupies  an  area  of about  24  sq.yd.  (20 sq.m). 


HUMMOCK:  A hillock of broken ice that has been forced upwards by pressure. May be fresh or weathered.  The  submerged  volume  of broken  ice  under  the  hummock,  forced downwards  by  pressure,  is  termed  a  hummock.  HUMMOCKY ICE is rough, uneven ice.

ICE BLINK:  Ice blink refers to a white glare seen on the underside of low clouds indicating the presence of ice which may be beyond the range of vision; can assist travelers in navigating the ice of the polar seas, since it gives a rough idea of ice conditions at a distance.


ICE FIELD: Area of pack ice consisting of floes of any size that is greater than 6 miles (10 km) wide.


ICEBERG:  A massive  piece of ice of greatly  varying  shape,  more  than  16  ft. (5  m)  above sea  level,  which  has  broken  away  from  a  glacier,  and  which  may  be  afloat or  aground.  Icebergs may be described as tabular, dome-shaped, sloping, pinnacled, weathered, or glacier bergs. 

LAND-FLOE or LAND ICE: See FAST  ICE


LEAD:  Any  fracture  or passageway  through sea  ice  that  is  navigable  by  surface  vessels.   


MELT POOL/POND:  As ice melts, the liquid water collects in depressions on the surface and deepens them, forming these melt ponds in the Arctic. These fresh water ponds are separated from the salty sea below and around it, until breaks in the ice merge the two.  (Wiki)

NEW ICE:  A general term for recently formed ice that includes frazil ice, grease ice, slush, and shuga, and is less than 4 inches (10 cm.) thick.  These  types  of ice  are  composed  of ice  crystals that  are only  weakly  frozen together  (if at  all)  and  have  a  definite  form  only  while  they  are  afloat.


NILAS:  A thin, elastic crust of ice bending easily on waves and swell.  Nilas has a matte surface and is up to 4 in (10 cm) thick.  Under pressure it thrusts into a pattern of interlocking fingers (see FINGER-RAFTED ICE). May be subdivided into dark nilas and light nilas.   

NIPPING ICE:  Ice is said to be nipping when it begins to close by reason of the action of winds or currents so as to prevent the passage of a vessel.


OLD ICE: Sea ice that has survived at least one summer's melt. Most topographic features on old ice are smoother than those on first-year ice.  May be subdivided into second-year ice and multiyear ice.   

PACK ICE:  a.k.a. ICE PACK.  Term used  in a  wide sense to include  any  area  of sea ice,  other than fast  ice, no  matter  what  form  it  takes  or how  it  is  disposed.


PACKED ICE:  Small pieces closed together and held by the pressure of wind and currents.   


PANCAKE  ICE:  Predominantly  circular  pieces  of ice  from  1  to  10 ft.  (30 cm to 3  m)  in diameter  and up to about 4 in (10  cm) in  thickness,  with  raised rims due  to the  pieces striking  against  one  another.  It may  be formed  on  a slight swell  from  grease  ice, shuga, or slush,  or as  a result of the  breaking  of ice  rind,  nilas,  or,  under severe  conditions  of swell or waves,  of gray  ice.  Sometimes  pancake  ice  forms  at some  depth,  at an  interface between  water bodies of different physical  characteristics,  from where it floats to the surface; it may  cover  wide  areas  of water  rapidly.   


POLYNYA:  Any nonlinear-shaped opening in the water but enclosed by ice.  Sometimes the polynya  is  limited  on  one side  by  the  coast  and  is  called  a shore  polynya,  or  by fast ice  and  is  called  a  flaw  polynya.  Some polynyi recur annually in the same position.   

PORRIDGE:  Small finely ground-up ice.  YOUNG PORRIDGE is porridge ice just forming.  (See Brash, Slush and Young Ice.)


RIDGE:  A line or wall of broken ice forced up by pressure; it may be fresh or weathered. The submerged volume of broken ice under a ridge, forced downwards by pressure, is termed an ice keel.   

ROTTEN  ICE:  Sea  ice  that  has  become  honeycombed  and  is  in  an  advanced  state  of disintegration.

SEA ICE: Any form of ice found at sea that has originated from the freezing of sea water.


SHUGA:  An accumulation  of spongy white  ice  lumps, a few  inches  (centimeters)  across; they  are  formed  from grease  ice  or slush  and  sometimes  from  ice rising  to  the  surface.   

SLACK ICE:  Ice that is detached so that it can be worked through.  Ice is said to be SLACKING when it begins to open so as to be navigable.

SLUSH:  Snow  that is saturated and mixed with water on land or ice surfaces,  or as  a viscous floating  mass  in  water  after  a  heavy  snowfall.

STORIS ICE:  'Storis' means 'Big Ice' in Norwegian. A wide belt of multi-year sea ice originating from the Arctic Ocean is normally present most of the year covering the entire east coast of Greenland. The intensity of the lows normally decrease in spring and summer, and may cause the multi-year ice to drift northwestwards along the Southwest Greenland coast in the West Greenland Current. (GEUS)

WATER SKY:  Water sky refers to the dark appearance of the underside of a cloud layer when it is over a surface of open water; can assist travelers in navigating the ice of the polar seas, since it gives a rough idea of ice conditions at a distance.

YOUNG  ICE:  Ice  in  the  transition  stage  between  nilas  and  first-year  ice,  4  to  12  in (10-30  cm)  in  thickness.  May be subdivided into gray ice and gray-white ice.  (NASA satellite photo)





SAILING TERMS

BESET (IN ICE): Situation of a vessel surrounded by ice and unable to move. (WMO Sea Ice Nomenclature)

BUCKING: Backing off and ramming ice in order to break a way through it.

CRUISING: Traveling back and forth across whaling grounds, westward in the morning and eastward at night in order to see whale spouts in a favorable light.

MADE FAST (TO ICE): Ship is moored to an ice floe as if it were a wharf.

TRACKING: Following along the edge of the ice pack.

WAKING: Following another vessel through leads and slack ice.

« Last Edit: September 15, 2016, 10:37:20 pm by DJ_59 »

Janet Jaguar

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Re: Sea Ice Types
« Reply #1 on: September 30, 2015, 11:49:49 pm »
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Janet Jaguar

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Re: Sea Ice Types
« Reply #2 on: September 30, 2015, 11:49:57 pm »
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