Formation of pancake ice in a wave field

Hayley Shen, Stephen AckleyClarkson University

andMark HopkinsUSACRREL

NSF/McMurdo Ground Station Science Workshop, Columbus OH, March 9-11, 2004

NSF OPP-9814968

• Pancake size• Rafting thickness• Early ice cover development• Heat transfer between air/ice

Result #1

Pancake Size

63s 55e October, 1hr from sunrise or sunset,floe size 30-50cm, from Australian Antarctic Division

How to determine limit size?

ALD

2

max

2/12

max

ALD

Bending failure mode:

Tensile failure mode:

Shen, Ackley, Hopkins 2001

2

31max 1

K

iceAgK

LD

)59.0,18.0(

)75.11,37.0(

2

1

K

K95% confidence interval

CRREL-2001winter, summer, 2003 summer

2

31max 1

K

iceAgK

LD

)59.0,18.0(

)75.11,37.0(

2

1

K

K95% confidence interval

Example: 100m wave of 5m amplitude yields 0.9m diameter pancakes.

y = 0.0668x0.5434

R2 = 0.81

0

10

20

30

40

50

60

0.00E+00 3.00E+04 6.00E+04 9.00E+04 1.20E+05 1.50E+05

L2/A (cm)

Dia

met

er (c

m)

CrrelError bar

y = 0.4193x0.358

R2 = 0.8618

0

5

10

15

20

25

30

35

0.E+00 3.E+04 6.E+04 9.E+04 1.E+05 2.E+05

L2/A (cm)

Dia

met

er (c

m)

HSVA

Error bar

HSVA-2002winter

Pancake ice formation

However….

Result #2

Equilibrium Ice Thickness from Wave Rafting

DDAShh

SDKh

DAKh

2' , 2,2'

, )'(''

2

3

22

Non-dimensional result

Dai, Shen, Ackley 2004

0.3 0.4 0.5 0.6 0.7 0.8-1.6

-1.4

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

Lower 95% Confidence Limit

Log(

h')

Log(S*D')

Upper 95% Confidence Limit

Fitted Line, Slope=2.07179

Wave Tank Experiment Results

4

2)2(' ,2'

ADSDhh

Computer Simulation

Computer Simulation (no friction)

Computer Simulation (friction)

Result #3

Early Ice Cover Establishment due to Wave Rafting

Some old models results

Hibler and Ackley 1983

Geiger 1997

Effects of h0 on Ice Cover Development (Earlier Appearance)

Dai, Shen, Ackley 2004, in preparation

Effects of Initial Ice Thickness on Ice Cover Development

Result #4

Air/Ice Heat Transfer in a Wave Field

Problem Definition

W

H

Ice

Water

Qia

cQ

bQ

1wQ 2wQ

Air

ExperimentsExperiments

Results

• Calm water cases• Wave cases• The standard deviation for wave cases is high,

suggesting that heat transfer coefficient may depend on wave parameters

• Enhanced turbulence, increased surface area, and a thin boundary layer above water/ice may be the reasons

)/(26.436.12 2mWhia

)/(32.1055.26 2mWhia

Dai, Shen, Ackley, 2004, in preparation

• Pancake ice size can be predicted from waves• Rafting thickness can also be predicted• Rafting thickness is important in early ice cover

development• Waves may greatly increase the thermodynamic

growth of ice• Waves may not always result in pancakes, the

critical condition has not been identified

We have found:

Next Steps

• Heat transfer between air/ice in a wave field• The critical condition for pancake formation• Incorporating Wave Effects into short and

long term climate models

We need…..

Accurate weather dataAccurate hydrographical data

Why?

Longitude

Latit

ude

-27

-27

-24

-24

-21

-21

-21

-21

-18

-15

-18

-18

-18

-15

-15

-15

-15

-15

-12

-9

-12

-12

-12

-12-9

-9

-9

-6

-6-6

-6

-3

-3

-3

00

135 140 150 16044

46

48

50

52

54

56

58

60

Longitude

Latit

ude

-33-30

-27

-27

-24

-24

-21

-21

-21

-18

-18

-18

-18

-18

-15

-15

-15

-15

-12

-12

-12

-12

-9-9

-9

-9

-6

-6-6

-6

-3

-3

-3

0

0

44135 140 150 160

60

46

48

50

52

54

56

58

Temperature of Dec. 30, 1993. Left panel is from NCEP real-time data, right from NCEP/NCAR Reanalysis data

(Wang, Shen, and Shen, Okhotsk Sea Conference, 2000)

Temperature difference between NCEP real-time and reanalysis data for 92-93 winter.

50 100 150 200Number of days from Nov. 1st, 1992

-3

-2

-1

0

1

2

3

Tem

pera

ture

diffe

renc

e(c

)

Longitude

0.05

0.050.05

0.15

0.15

0.25

0.25

0.35

0 .35

0.3 5

0.35

0.4 5

0.45

0.45

0.55

0.65

Latit

ude

135 140 145 150 15544

49

54

59

Ice concentration. Date: March 5, 1993. Input data: NCEP real-time.

Longitude

0.0 5

0 .05

0.150.25

0.45

0 .5 5

0.650.75

0.75

Latit

ude

135 140 145 150 15544

49

54

59

Ice concentration. Date: March 5, 1993. Input data: NCEP Reanalysis.

Observed buoy trajectories and simulated ice floe trajectories in the winter of 1993-94.

A lot of work to be done!Collaborations!