Winter sea-ice thicknesses in the Weddell Sea

and their variability over the past 24 years

Sandra Schwegmann1, Priska Hunkeler1, Stefan

Hendricks1, Peter Lemke1, Christian Haas2, Thomas

Krumpen1, Robert Ricker1

1Alfred Wegener Institute for polar and marine research

2York University

ANT-XXIX/6: the recent winter experiment

ANT-XXIX/6

08.06.-12.08.13

Cape Town – Punta Arenas

Winter experiment

9 drilling stations

- Sea ice thickness

- Freeboard

- Snow depth

Objectives

Regional Sea Ice Thickness Distribution

Thermodynamic & Dynamic Ice Growth

Remote Sensing Validation Data

CryoSat-2 SMOS

Method Development

Improved Resolution (1D ���� 2D)

Objectives

Regional Sea Ice Thickness Distribution

Thermodynamic & Dynamic Ice Growth

CryoSat-2 SMOSComparison to other winter data

Distribution 1992 vs. 2013

Sea ice thickness Snow depth

70

60

50

40

30

20

10

0

Fre

quency 2

013

240220200180160140120100806040200

Sea ice thickness (cm)

110

100

90

80

70

60

50

40

30

20

10

0

Fre

quency 1

992

2013

1992

60

50

40

30

20

10

0

Fre

quency 2

013

1009080706050403020100

Snow depth (cm)

160

140

120

100

80

60

40

20

0

Fre

quency 1

992

2013

1992

• Sea-ice thickness distribution comparable

• Snow depth much higher in 2013

Retro Drilling-GEM comparison

0

20

40

60

80

100

120

140

160

180

200

21. Jun. 26. Jun. 1. Jul. 6. Jul. 11. Jul.

RD TIT

GEM TIT

RD sdev

GEM sdev

RD mode

Gem Mode

Winter - early spring expeditions

ANT-VIII/2

06.09. – 31.10.1989

Weddell Sea, Spring

ANT-X/4

21.05. – 06.08.1992

Weddell Sea, Winter

ANT-XXIII/7

24.08. – 29.10.2006

Western Weddell Sea, Winter-Spring

ANT-XXIX/6

08.06. – 12.08.2013

Weddell Sea, Winter

ANT-XXIX/7

14.08. – 16.10.2013

Western Weddell Sea, Winter-SpringANT-VIII/2Augstein et al., Ber. Polarforsch. 84(1991)

Sea-ice thickness comparison

800

700

600

500

400

300

200

100

0

3.53.02.52.01.51.00.50.0

24

22

20

18

16

14

12

10

8

6

4

2

0

1989

2006

2013 (ANT-29/7)

70

60

50

40

30

20

10

0

Fre

quency 2

013

240220200180160140120100806040200

Sea ice thickness (cm)

110

100

90

80

70

60

50

40

30

20

10

0

Fre

quency 1

992

2013

1992

• Sea-ice thickness distribution comparable between 1989 and 2013

• 2006 shows higher sea-ice thickness

Snow depth comparison

1.41.21.00.80.60.40.20.0

900

800

700

600

500

400

300

200

100

0

50

45

40

35

30

25

20

15

10

5

0

1989

2006

2013 (ANT-29/7)

60

50

40

30

20

10

0

Fre

quency 2

01

3

1009080706050403020100

Snow depth (cm)

160

140

120

100

80

60

40

20

0

Fre

quency 1

992

2013

1992

• Snow depth much higher than in every other year

Freeboard comparison

50

40

30

20

10

0

Fre

quency 2

01

3

-30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30

Freeboard (cm)

60

55

50

45

40

35

30

25

20

15

10

5

0

Fre

quency 1

992

2013 (ANT-29/6)

1992

500

450

400

350

300

250

200

150

100

50

0

Fre

quency 1

989

-0.30 -0.20 -0.10 0.00 0.10 0.20 0.30

Freeboard (m)

14

12

10

8

6

4

2

0

Fre

quency 2

006/2

013

1989

2006

2013 (ANT-29/7)

• Freeboard shifted to lower or more negative values in 2013

• Interesting feature: 2006 shows very low, strongly negative

shifted freeboard despite of less snow and thicker ice compared

to other years!

Sea ice extent variability

Image source: http://nsidc.org/data/seaice_index/

Summary

• Sea ice thicknesses comparable to former winter/spring

experiments

• Snow depth particularly high in 2013

• Freeboard generally more negative with higher snow

coverage

• Exception: 2006

• Comparison with model data

• Analysis: Does the snow save the sea ice

Outlook