pp ice number 1

8/18/2019 PP ICE Number 1

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A study---

by capt. francis t. gauci



Ice

is found at high latitudes

in both hemispheres but

because of their physical dissimilarities

the climatic and ice regimes

of the Arctic and Antarctic regions

differ greatly.



Arctic Region :

• is confined to sea areas

off E and W coasts of Greenland

and

• off eastern seaboard of Canada• remains completely coered by pac! ice

throughout the year



Arctic "cean ice



Arctic Ice



Arctic #asin :

• is an area of ocean $%%%m deep• coered by $.&m ice thic! • annual mean temp. at '.(. -)%deg C

• lo*est recorded in Arctic #asin -&%deg C

Antarctica :

• has an ice-cap up to $%%%m tic! • annual mean temp. at +.(. -,deg C• lo*est recorded -.$deg C



Antarctica Region :

• ice-cap coering Antarctica constitutes %/

of the permanent ice of earth• the ice constituting the ice-cap moes to*ards the coasts

• the icebergs form from glaciers and ice-sheles• the icebergs are found in a *ide belt

surrounding the continent• the greater part of pac! ice surrounding this region

melts each summer • this region is at a lo*er latitude than its arctic counterpart



Reference :

• +ea Ice 'omenclature : W0" 12%

• 0arine3s "bserer3s 4andboo!

• 5he 0ariner3s handboo! '( 1%%



Classification of Ice :

• +ea Ice : free6ing of sea *ater

• Icebergs : fresh *ater

• Rier Ice : fresh *ater



7ormation of Ice :

Fresh water and salt water

do notnot free6e in the same manner.

+alinity is measured in parts81%%%

• *here there is discharge of rier *ater9

salinity is much less

• the #altic sea is 1%81%%% through the year



7ree6ing process :

salinity effectslo*ering of free6ing temp.

density of *ater



7resh *ater :

Cooling from surface

o*ering of temp.

0a;imum density at ,deg C

If a body of fresh water is cooled to 4deg C throughoutits depth, convection ceases.



+alt *ater :<elay in lo*ering of temp. to free6ing temp.

is much more prolonged.

Example : off S Svalbald !! convection prevents

formation of ice throughout winter due to deep warm water

"despite very low air temp.#



Maximum density of sea water

of average salinity occurs at

temp. below freezing point.

Refer to follo*ing slide.



mcast



• *ater *ith salinity = ),.2 parts81%%% has

maximum density reached before free$ing temp.

• Water *ith salinity > ),.2 parts81%%% has

its free$ing point reached before density attains

the theoretical maximum value.



5he greatest delay in reaching the free6ing temp.

occurs *hen the sea *ater is initially at an

almost uniform density9

throughout its depth.



At a temp. bet*een

%deg C and free$ing 9

ariations in density are more dependent

on ariations of salinity

than on changes in temp.



In Arctic #asin :

+alinity discontinuity bet*een the surface layer

?Arctic Water@ and

the underlying more saline Atlantic *ater.

Cooling of the surface *ater around the periphery of #asin9

and *ithin regions of open *aters9

leads to conection in a shallo* layer *hich

may e;tend to only &% m in depth.



7irst indication of ICE :

appearance of ice spicules or plates

?ma;imum dimension up to ).&cm@

in the top fe* centimeters of *ater.

• 7RAI ICE : forms in large Buantities

and gie the sea an oily appearance.

• As cooling continues the fra6il crystals coalesce

to form GREA+E ICE *hich has a matt appearance.



nder near free6ing9 but as yet ice-free conditions9

sno* falling on the surface and forming ++4

may induce the sea surface to form a layer of ice.

5hese forms may brea! up under the action of *ind

and *aes to form +4GA.

'EW ICE :

7RAI ICEDGREA+E ICED++4D+4GA



'EW ICE :

7RAI ICE

DGREA+E ICE

D ++4

D +4GA



0elt pools deeloping as ice recedes during summer.

Coast from 0urmans! to #earing +ea.



With further cooling :

sheets of ICE RI'< or 'IA+ are formed9

depending on the rate of cooling

and on the salinity of the *ater.

ICE RI'< is formed *hen *ater of

lo* salinity free6es slo*ly9

resulting in a thin layer of ice*hich is almost free of salt.



When *ater of high salinity free6es9

especially if the process is rapid9

the ice contains poc!ets of salt *ater9

giing it an elastic property*hich is characteristic of 'IA+

'IA+ : dar! 'IA+ : = &cm thic!

light 'IA+ : > &-1%cm thic!



Foung ICE :

action of *ind and *aes may brea! up

ice rind and nilas into

(A'CAE ICE

*hich later free6es together and thic!ensinto GREF ICE

and GREFDW4I5E ICE

the latter attaining thic!ness up to $%cm.



F"'G ICE :

(A'CAE ICE

DGREF ICE

DGREF-W4I5E ICE

rough weather may break this ice up into

ICE CAE+ or 7"E+



(anca!e ice #earing +ea



Foung ice ara +ea



Ice floe 'orth #earing +ea



Collecting fresh *ater



'e;t stage of deelopment :

7IR+5-FEAR ICE

thin

medium 2%-1)%cm thic!

thic! up to )m by end of *inter



7irst year ice #earing +ea



+hould the first year ice surie

the summer melting season

?e;ample : Arctic #asin@

it is designated as

+EC"'<DFEARDICE

at the onset of the ne;t *inter.



+ubseBuent persistence through summer melts

*arrants the description 05IDFEARDICE

*hich9 after seeral years9

attains a ma;imum thic!ness of $.&m

?*hen accretion of ice in *inter balances

the loss due to melting in summer@



5he buoyancy of leel sea ice is such that

appro;imates ?182@

of the total thic!ness floats aboe the *ater.

Ice increases in thic!ness from belo*

as the sea *ater free6es on the undersurface of the ice.

5he rate of increase is determined by

the seerity of the frost and by its duration.



HAccumulated frost degree-days3

is the total of daily mean air temps.9

belo* %deg C9

summed oer the period of frost

--refer to the follo*ing graph--



As ice becomes thic!er9

the rate of increase in thic!ness

diminishes9 due to the insulating effect of the ice

?and its oerlying sno* coer@

E5RE0E C"'<I5I"'+ :

temp. -$% to -,% deg C

thic!ness 1%cm in ), hours

thic!ness 1cm in , hours.



Antarctic Region ?more than the Arctic@

?i@ *hen sno* coer ?> &%cm@

*eight of sno* may depress

the original ice layer belo* sea leelso that sno* becomes *ater-logged.

In *inter the *et sno* gradually free6es9

thus increasing the depth of the ice layer.



Antarctic Region :

?ii@ the super-cooling of *ater

as it flo*s under the deep ice sheles9

typical of Antarctic coastline.

5he super-cooled *ater is preented from

free6ing by pressure at this depth.

5he flo* of *ater under the ice sheles

is often igorous9 the conseBuent turbulenceresulting in some of the super-cooled *ater

rising to*ards the surface

as it leaes the icinity of the ice-sheleJ..



JJthe conseBuent

reduction of pressuremay lead to the rapid formation

of fra6il ice

in the near surface *ater.

5he same mechanism can result inthe accumulation of a

relatiely deep layer

of porous ice

beneath an original ice layer.



E;ample :

Recently bro!en fast ice oer ,m thic!encountered on the approaches to

Enderby and in the southern autumn ?0arch@

*as obsered to consist of

only $%cm of solid ice

and ,m of porous ice9

the *hole layer offering

little resistance to for*ard progress.

?an effect almost entirely confined to

the fast-ice 6one@



+mall bergy bits



#ro!en fast ice



Edge of pac! ice



Ice floes 'orth #earing +ea



Ice and fog



Glacier Alas!a



+ea ice 5igaria! Island



+ea ice hummoc!

Glacier



Foung ice ara +ea

Winter sea-ice #eaufort +ea



Ice brea!er at anchor side ie*

7ront ie*+ide ie*

Ice brea!er at anchor



5he underside of ice is reealed in this rare glimpse from belo*9

sho*ing yello*ish clouds of algae illuminated by stabs of sunlight.



Arctic Pack



The Arctic pack, which averages 3 to 6

m (10 to 20 ft) thick during winter,circles the Arctic cean in a clockwisedirection! "ost #oes sta$ in the Arcticcean for % or more $ears, &ut the$eventuall$ escape, mainl$ &etween'pit&ergen and reenland, and ma$#oat as far south as *celand &eforecompletel$ melting awa$!

*n certain places in the Arctic pack, the +amming and crushing of #oes formpressure ridges and hummocks thatma$ rise % m (16 ft) or more a&ove the

general level of the pack! *rregular



/ack ice, made of froen salt water, iscomposed of pieces of ice of various shapes,sies, and ages that are free to drift under the

in#uence of winds and ocean currents! Anindividual piece of ice in the pack is called a #oeand can var$ from a few meters to more than 10km (several feet to more than 6 mi) in length!

The two largest areas of pack ice are in and nearthe Arctic cean and in the Antarctic region!



Antarctic Pack

The Antarctic pack entirel$ surroundsthe Antarctic continent at the end ofwinter and ma$ etend for severalhundred kilometers north of the coast!*ts edge advances northward during thewinter months and retreats southwardduring the summer! The Antarctic pack is

1 to 2 m (3 to ft) thick, and theindividual #oes are 1 or 2 $ears old!



An ice&erg is a large piece of ice that

has calved (&roken o) from theterminus of a glacier (see glaciers andglaciation) into a &od$ of water! "ostice&ergs are found in the ocean, &ut all

are composed of freshwater ice! The$ areusuall$ white, &lue, or green, althoughsome are &lack &ecause of rock materialthe$ contain!

l i



The glaciers of Antarctica and reenlandare the sources of most ice&ergs! The largest

ice&ergs are found in Antarctica! The !'!4oast uard ice&reaker Glacier measured onethat was 333 km (205 mi) long and -6 km (60mi) wide! The$ ma$ etend downward 300 m

(1,000 ft) and reach a height of more than 60m (200 ft)! n the average, 6 of the volumeof an Arctic ice&erg and 7% of ice&ergs ofAntarctic origin are su&merged! The degree ofsu&mergence depends on the densit$, rock

content, and shape of the ice&erg!



Glacier melting



n Apr! 17, l-12, the Titanic, then the largestship in the world, ran into a small ice&erg on hermaiden vo$age across the Atlantic and sank, resultingin the deaths of 1,%03 people! 8uring 9orld 9ar ** theAllies considered anchoring a #at: topped Antarctic

ice&erg in the Atlantic to serve as a landing ;eld forplanes involved in su&marine warfare! 'everal nationshave set up research stations on #oating ice&ergs(see, for eample, <letcher=s *ce *sland)! 'erious

thought has &een given to the possi&ilit$ &oth ofharvesting ice from ice&ergs and of shipping wholeice&ergs to arid countries for use as a source of freshwater!



An ice&reaker is a vessel used for



An ice&reaker is a vessel used forclearing a passage through ice:&ound waters!

The earliest such vessels were used on>ussia=s ?ake @aikal and on the @altic 'ea!ne of the ;rst and most successfulice&reakers was the Ermak , &uilt for the>ussian government and launched on the

>iver T$ne in ngland in 15-5! The vessel hada steel hull and an enormousl$ strengthened&ow, &uilt with a ver$ gradual slope upwardfrom &elow so that the ship could ride up

onto the ice and use its weight to &reak infrom a&ove! "ost present:da$ ice&reakersuse the same t$pe of &ow constructionB man$of them are also eCuipped with a &u&&lers$stem that pumps a la$er of friction:reducin air &etween the hull and the ice!



The ''> long held the lead in ice&reakertechnolog$, with a #eet of more than %0 ships and

tugs in the 1-50s! The 'oviet ice&reaker Lenin,commissioned in 1-%-, was the world=s ;rstnuclear:powered surface ship! The Arktika (1-)was the ;rst surface vessel to navigate passage to

the .orth /ole, traveling from "urmansk across the@arents 'ea and the Arctic cean! The lastgeneration of 'oviet nuclear ice&reakersDthe resultof a +oint <innish:'oviet design eort in the late1-50sDwere two shallow:draught ships, &uilt to

clear ice in the river estuaries of the @altic!

(.uclear ice&reakers can operate up tothree $ears without refueling!)



<inland designs man$ of the world=s ice&reakers,including such advanced vessels as Australia=s

Aurora Australis (1--0), which sails Antarcticoceans on research epeditions! The nited 'tatesoperates a small num&er of ice&reakers, primaril$on the reat ?akes and on northern rivers and

har&ors! The two !'! /olar 4lass ice&reakersDoneof which traversed the .orthwest /assage in1-5%Dalso function as research vessels in Arcticand Antarctic waters! *n 1--7 a +oint !'!:4anadian ice&reaker epedition traversed the

Arctic from west to east for the ;rst time and&ecame the ;rst .orth American surface ships toreach the .orth /ole!



Wor!ing 'orth in Winter months

is dangerous

because of the chance of

your essel icing up

because of ice accretion



5here are seeral reasons for ice accretion9 these areK

?1@ +pray hitting the essel *ith the air temperature being at least minus )degrees.

?)@ 7og free6ing on the structure of your essel.

?$@ Rain 7ree6ing on the structure of your essel.

?,@ +eas entering your essel and free6ing up.

?&@ 7resh *ater lea!ing or being discharged from

a pipe on your essel.

If l t t t i th h i ti th



If your essel starts to ice up through ice accretion then

do the follo*ingK

?1@ 5urn the essel around and head +outh

to*ard a *armer climate.

?)@ 0inimise the spray coming onto your essel

by slo*ing your essel do*n

?$@ If your essel is listing to starboard9

then ta!e the ice off the port side first9

youLll gie your essel a bigger list9 but the centre of buoyancy *ill moe out also and

thus you *ill hae a bigger righting leer.

5h t t



5he a* states

if you encounter ice accretion

on your essel

that *as not issued *ith the shipping forecast9you mustK

?1@Inform all ships in the area

?)@ Contact the Coastguard

Never ever take chances with ice accretion,



this can and will severely affect

your vessels stability,

vessels have capsized because

of the ANGLE OF LOLL effect

that ice accretion has on the vessel,

the vessel will become top heavy

as the entre of Gravity nears!meets of"oes above the #etacentre$

%&he vessel with have an

'N(&A)LE E*'+L+)+'#-$



Ice accretion aboard the research ship in the Arctic "cean

+ea Ice JJ..A



•+ea Ice is diided into two main types according to its mobility.

• "ne is (AC ICE9 *hich is reasonably free to moe under

the action of the *ind and current.

• 5he other is 7A+5 ICE *hich does not moe. Ice first forms near the coast and spreads sea*ards. A certain *idth of fairly

leel ice9 depending on the depth of the *ater9 becomes fast

to the coastline and is immobile.5he outer edge of the fast ice

is often located in the icinity of the )&-metre contour.

A reason for this is that *ell-hummoc!ed and ridged ice may

ground in these depths and so form off-shore anchor points

for the ne* season3s ice to become fast.

+ea Ice JJ..#



• #eyond this ice lies the pac! ice *hich has formed9 to a small

but important e;tent9from pieces of ice *hich hae bro!en

off from the fast ice. As these spread sea*ards they9 together

*ith any remaining old floes9 facilitate the formation of 'EW9

and later F"'G ICE in the open sea.

• 5his ice 9 as it thic!ens9 is constantly bro!en up by the *ind

and *aes so that the pac! ice consists of ice of all si6es and

ages from giant floes of seeral years3 gro*th to the seeral

forms of ne* ice *hose life may be measured in hours.

<eformation of IceJJA



• nder the action of *ind9 current and internal stress the pac! ice is constantly in motion.

• Where the ice is subMected to pressure its surface

becomes <E7"R0E<.• In the ne* and young ice this may result in RA75I'G as an ice sheet oerrides its neighbor.

• In thic!er ice it leads to the formation of

RI<GE+ and 400"C+ according to the pattern

and strength of the conergent forces.

<eformation of IceJJ#



• <uring the process of ridging and hummoc!ing9*hen large pieces of ice are piled up aboe the general

ice leel9 ast Buantities of ice are forced do*n*ard to

support the *eight of ice in the ridge or hummoc!.• 5he do*n*ard e;tension of ice belo* a ridge is!no*n as an ICE EE9 and that belo* a hummoc! is

called a #00"C .

5he total ertical dimensions of these features may reach

&& metres9 appro;imately 1% metres sho*ing

aboe the sea leel.• In shallo* *ater ice floes piled up against the coastline

may reach 1& metres aboe mean sea leel.

<eformation of Ice C



<eformation of IceJJC

• CRAC+9 EA<+ and

("F'FA+ ?open areas *ithin an ice field@

may form after pressure *ithin the ice has been rela;ed.

When these openings occur in *inter they rapidly

become coered by ne* and young ice *hich9 giensufficient time9 *ill thic!en into first-year ice and

cement the older floes together.• #efore the first year stage is reached9 the younger ice

is subMected to pressure as the older floes moe together9resulting in the deformation features already described.

<eformation of IceJJ<



• "ff-shore *inds drie the pac! ice a*ay from the coastline

and open up a +4"RE EA<9 *hich is a naigable passage

bet*een the main body of the pac! ice 9 and the shore.

• In some regions *here off-shore *inds persist through theice season9 locali6ed moement of shipping may be possible

for much of the *inter.

• Where there is fast ice against the shore9 off-shore *indsdeelop a lead at the boundary9 or 7AW as it is !no*n9

bet*een the fast ice and the pac! ice: this opening is called a

7AW EA<.

<eformation of IceJJE



• In both types of lead9 ne*-ice formation *ill beconsiderably impeded or een preented if the off-

shore *inds are strong.

• "n most occasions ne* and young ice forms in the leadsand *hen *inds become on-shore the re-fro6en lead closes up

and the younger ice is completely deformed.

• 7or this reason the fla* and the coast9 especially *hen

the on-shore *inds preail9 are usually mar!ed by tortuous

ice conditions.



Ridges (olynya

+ea Ice hummoc!



Winter sea ice #eaufort +ea

Clearance of Ice A



Clearance of IceJ..A

• 5he clearance of ice in summer may occur in t*o different *ays.• 5he first9 applicable to pac! ice only9 is the direct remoal

of the ice by the *ind or current.

• 5he second method is by melting in situ *hich may be

achieed in seeral *ays.

• Wind plays a part in that *here the ice is *ell bro!en *ae action

*ill cause a considerable amount of melting een if the sea

temperature is a little aboe the free6ing point.

• Where pac! ice is not *ell bro!en or *here there is fast ice9

the melting process is dependent on the incoming radiation.

Clearance of IceJ..#



• In the Arctic in *inter the ice becomes coered *ith sno*

to a depth of about $% to N% centimeters.• While this sno* coer persists9 almost %/ of the

incoming radiation is reflected bac! to space.• Eentually the sno* begins to melt as air temperatures rise

aboe %deg C in early summer and the resulting fresh *ater

forms puddles on the surface.• 5hese puddles absorb about N%/ of the incoming radiation

and rapidly *arm up9 steadily enlarging as they melt thesurrounding sno* and9 later9 the ice.

Clearance of Ice C



Clearance of IceJ..C

• Eentually the fresh *ater runs off or through the ice

floe and 9 *here the concentration of the pac! ice is high9

it *ill settle bet*een the ice floe and the underlying sea *ater.

• At this stage the temp. of the sea *ater *ill still be belo*

%deg C so that the fresh *ater free6es onto the undersurface of the ice9 thus temporarily reducing the melting rate.

• 0ean*hile as the temp. *ithin the ice rises9

the ice becomes riddled *ith brine poc!ets.

• It is considerably *ea!ened and offers little resistance to

the destructie action of *ind and *aes.

Clearance of IceJ..<



• At this stage the fast ice fast brea!s into pac! ice andeentually the ice floes9

• *hen they reach an adanced stage of decay9

brea! into small pieces called #RA+4 ICE9

the last stage before melting is complete.• Wind9 *aes9 and rising temperatures combine

to clear the ice from areas *hich are affected

by first-year ice.



+pring melting ice

Clearance of Ice E



Clearance of IceJ..E

• 5he brea!up of fast ice by paddling seems to be

limited to the Arctic regionK• it has not been obsered in the Antarctic *here sno*

depths are usually greater ?i.e. &%cm-1m.@

• in the Antarctic9

?i@ due to the presence of the surrounding

turbulent ocean9 the fast ice is more often bro!en up by

the action of ocean s*ell9

particularly after the pac! ice has been remoed by the

off-shore *inds *hich preail in the region.

?ii@ presence of diatoms in the lo*er layers of the fast ice.



0oement of IceJ..A



• pac! ice moes under the influence of *ind and current• fast ice stays immobile• the *ind stress on the pac! ice causes the floes to moe

in a do*n*ind direction

• Coriolis force causes the floe to deiate• the ice moement due to *ind drift is appro;imately

parallel to the isobars• the speed of moement9 due to *ind drift9 aries not

only *ith the *ind speed but also *ith the concentration

of pac! ice and the degree of ridging.

0oement of IceJ..#



• in ery open pac! ice there is much more freedom

to respond to the *ind than in close pac! ice *here

free space is ery limited.• H*ind-drift factor3 is the ratio of the ice drift to

geostrophic *ind speed.

• 5he total moement of pac! ice is the resultant of*ind-drift component and current component.

• +ince most of the ice is immersed in the sea

it *ill moe at full current rate e;cept in narro* channels.• Ice moement *ill be considerable9 if *ind blo*s in same direction as current.

?e;ampleJGreenland +ea9 #arents +ea off abrador@

Ice at the Ice Edge



g

When *ind blo*s from the open sea on to the pac! ice9

it compacts the floes into higher concentrations

along the ice edge.

When the *ind blo*s off the ice 9 the floes moe out intothe open sea at arying rates9 depending on there :

roughness and age



.revailin" surface currents in the Arctic Ocean and north/eastern parts of the

Atlantic Ocean$ &he circulation to the north of Alaska is known as the

)eaufort (ea Gyre$ &he dotted lines indicate mi0ed water$

0o ement of (ac! Ice in the Antarctic



0oement of (ac! Ice in the Antarctic

• 5he action of *ind and current around the coast of

Antarctica imparts a northerly component to the

moement of pac! ice so that it eentually carried

into *armer *aters of the +outhern "cean Current *here it melts.

• 5he pac! ice of this hemisphere is therefor mainly first-year ice.

• It is only in a fe* areas9 e;. Weddell and #ellingshausen +eas9

*here the action of the *ind carries the ice on to the coasts9and second and multi-year ice is commonly found.



Ice #ergs

Antarctica



Iceberg



Iceberg #eaufort +ea



Ice flo* 'orth #earing +ea



"pen Ice

pp ice number 1

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