Loset Ice Physics

8/8/2019 Loset Ice Physics

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Ice Physics

Sveinung Lset, prof.Department of Civil and Transport Engineering,

Marine Civil Engineering Group, NTNUUNIS, Arctic Technology


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The water molecule

When oxygen makes 2 covalent bonds as in water, HWhen oxygen makes 2 covalent bonds as in water, H22O, itO, it

is surrounded by four electron pairs. Ris surrounded by four electron pairs. ROOOO = 2.97= 2.97 , R, ROHOH ==

0.960.96

2 bonding pairs and 2 lone pairs, in roughly tetrahedral2 bonding pairs and 2 lone pairs, in roughly tetrahedral

arrangement (104.5arrangement (104.5))


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Hydrogen bonding

Hydrogen bondHydrogen bond a chemical bonding which arises when aa chemical bonding which arises when a

H atom lies between 2 of the highly electronegative atomsH atom lies between 2 of the highly electronegative atoms

F, O or NF, O or N

Accounts for the tetrahedral bonding of the molecules inAccounts for the tetrahedral bonding of the molecules in

iceice

In the H bond the H nucleus remains covalently bonded toIn the H bond the H nucleus remains covalently bonded to

one of the O atomsone of the O atoms

The strength of the hydrogen bond is intermediate betweenThe strength of the hydrogen bond is intermediate betweenthat of a covalent bond and the residual vanthat of a covalent bond and the residual van derderWaalsWaals

interactioninteraction --> a melting point mid> a melting point mid--way between those of away between those of a

covalent crystal like diamond and a rare gas like neoncovalent crystal like diamond and a rare gas like neon


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Molecular structureMolecular structure


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Continuous molecular structureContinuous molecular structure


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Defects in iceDefects in ice

Defects Type Remarks

Pointdefects VacancyInterstitialH3O

+

OH-

D-defect

L-defectElectron excitationImpurity molecule

Water molecule missing from ice structureWater molecule not at a structure positionWater molecule with additional protonWater molecule with proton missingO-O bond with two protons on or near it.

O-O bond with no proton on itPlace where an electron is excited from its ground stateMolecule other than H2O on a H2O site

Line

defects

Dislocation Boundary line of a region where part of the crystal has

been displaced relative to another part

Planedefects

Stacking fault A plane on which the stacking sequence is not what itshould be in the structure


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Defects in iceDefects in ice


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Water -> Ice

Triple pointTriple point 3 phases are in equilibrium: T = 273.16 K, p =3 phases are in equilibrium: T = 273.16 K, p =

611.7 Pa611.7 Pa

HH22O expands on freezingO expands on freezing

Other examples: Silicone, germaniumOther examples: Silicone, germanium

Max density at T = 3.98Max density at T = 3.98CC The crystals reveal the hexagonal symmetry of the crystalThe crystals reveal the hexagonal symmetry of the crystal

lattice of icelattice of ice

The cThe c--axis [0001] is the hexagonal axisaxis [0001] is the hexagonal axis


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Development of ice coverDevelopment of ice cover

Growth sequence


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Growth sequence of ice crystalsGrowth sequence of ice crystals

(a) (b)


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Growing of isolated crystalsGrowing of isolated crystals

Initial discs, size 1 mm

Stellar ice crystals


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Pancake icePancake ice


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Phase relation of sea ice, S = 34.3Phase relation of sea ice, S = 34.3 pptppt


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Sea ice crystal structureSea ice crystal structure


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Structure of firstStructure of first--year sea iceyear sea ice


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Thin section showing cellular substructureThin section showing cellular substructure

Spacing between brine layers, ~ 0.6 mm


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Types and stages of level iceTypes and stages of level ice

Type SubdivisionNew ice Recently formed ice.

> Frazil ice: Fine spicules or plates of ice, suspended in water.> Grease ice: A later stage of freezing than frazil ice when the crystals have coagulated. Grease icereflects little light, giving the sea a matt appearance.> Slush: Snow which is saturated and mixed with water on land or ice surfaces.

> Shuga: An accumulation of spongy white ice lumps, a few centimetres across. They are formedfrom grease ice or slush.

Nilas A thin elastic crust of ice (< 10 cm thick), easily bending on waves and swell.> Dark nilas (< 5 cm thick).> Light nilas (> 5 cm thick).

Pancake ice Predominantly circular pieces of ice from 0.3-3 m in diameter, and up to about 10 cm in thickness,

with raised rims due to the pieces striking against one another. It may be formed on a slight swellfrom grease ice, slush or shuga or as a result of the breaking of ice rind, nilas or, under severeconditions of swell or waves, of grey ice.

Young ice Ice in the transition stage between nilas and first-year ice, 10-30 cm thick.> Grey ice young ice 10-15 cm thick. Less elastic than nilas and breaks on swell. Usually raftsunder pressure.

> Grey-white ice young ice 15-30 cm thick. Under pressure more likely to ridge than to raft.First-year ice Sea ice of not more than one winters growth, developing from young ice, thickness 0.3 m 2 m.

> Thin first-year ice (0.3-0.7 m thick)> Medium first-year ice: first-year ice 0.7-1.2 m thick.> Thick first-year ice: first-year ice over 1.2 m thick.

Old ice Sea ice that has survived at least one summers melt. Most topographic features are smoother thanon first-year ice.> Second year ice: Old ice which has survived only one summers melt.> Multi-year ice: Old ice up to 3 m or more thick which has survived at least two summers melt.


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Types of ice surface featuresTypes of ice surface features

Type Subdivision

Level ice Sea ice which is unaffected by deformation.

Deformed ice A general term for ice which has been squeezed together and in places forced upwards ordownwards.

Rafted ice Type of deformed ice formed by one piece of ice overriding another.

Ridge A line of ice formed by pressure or shear:> New ridge: Ridge with sharp peaks and slopes of sides usually about 40> Weathered ridge: Ridge with peaks slightly rounded and slope of sides usually 30-40. Individual

fragments are not discernible.> Very weathered ridge: Ridge with peaks very rounded, slope of sides usually 20-30.> Aged ridge: Ridge which has undergone considerable weathering.> Consolidated ridge: A ridge in which the upper parts of the ridge has frozen together.

Rubble Ice piles haphazardly one piece over another in the form of ridges or walls.

Stamukha Grounded ridge.

Hummock A hillock of broken ice which has been forced upwards by pressure. May be fresh of weathered. Thesubmerged volume of broken ice under the hummock, forced downwards by pressure, is termed abummock.

Hummocked ice Sea ice piled haphazardly one piece over another to from an uneven surface. When weathered, has

the appearance of smooth hillocks.


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Physical and thermal propertiesPhysical and thermal properties

Ice/snow Parameter Value

Freshwaterice

Density (kg/m3)Porosity (%)Latent heat of fusion (kJ/kg)

Specific heat capacity (kJ/kgC)Thermal conductivity (W/mC)

916.80.5-5333.4

2.112.21

Snow Density (kg/m3)Latent heat of fusion (kJ/kg)Specific heat capacity (kJ/kgC)Thermal conductivity (W/mC)

300-4003342.090.25


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Effects of temperatureEffects of temperature

1-E

2a,b- T

3a,b- c


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UniaxialUniaxial strength vs. temperaturestrength vs. temperature


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Tensile strength vs. temperature (V)Tensile strength vs. temperature (V)


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Tensile strength vs. temperature (H)Tensile strength vs. temperature (H)


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Salinity vs. depthSalinity vs. depth

Salinity, g/l

-100

-80

-60

-40

-20

0

0 2 4 6 8 10

Depth,cm

20.04.2004

21.04.2004


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PorosityPorosity

0

49.180.001 ( 0.53)

1

b a

b

a

V V

V S

T

V

= +

= +

=


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Brine volume vs. depthBrine volume vs. depth

0

20

40

60

80

100

120

6 7 8 9 10 11 12

Brine volume, %

Depth,cm

Core 1

Core 2


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UniaxialUniaxial compressive strength vs. brine porositycompressive strength vs. brine porosity


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UniaxialUniaxial tensile strength vs. brine porositytensile strength vs. brine porosity


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Columnar sea iceColumnar sea ice

0.2237 1 ( )27c Pa

=

H loaded

0.22160 1 ( )2

c Pa

=

V loaded


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Granular sea iceGranular sea ice

0.2249 1 ( )28

cPa

=


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Flexural strengthFlexural strength

1.76 exp 18.6 ( )f

Pa =

3 26

/12 2

b bf

F L F Lh Bh Bh

= =


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Modulus of elasticity in bendingModulus of elasticity in bending

3

34f FLEBh=


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Tensile strength (V and H)Tensile strength (V and H)

2.2 1 ( )0.031

1.0 1 ( )0.014

tv

th

Pa

Pa

=

=

S ( )Sh t th (V d H)


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Shear strength (V and H)Shear strength (V and H)

1.5 1 ( )39

Pa

=

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