Sea Ice

Walt Meier

Contributors to Sea Ice Section:J. Comiso, F. Nishio, T. Agnew, J. Yackel,

M. Tschudi, R. Kwok, R. DeAbreu, J. Falkingham

3rd IGOS Cryosphere Theme Workshop, Noordwijk, 16 – 18 October 2006

Importance of Sea Ice Observations

• Climate– Albedo feedback– Heat/moisture transfer between

ocean and atmosphere– Salt flux between ice and ocean– Key indicator of current climate

change in the Arctic

• Modeling – GCM, regional, forecasting

• Operations – navigational safety

• Indigenous populations• Wildlife

Sep 1

97

9-1

983

Sep 2

00

2-2

006

SSM/I, Passive Microwave

Sea Ice Parameters• Extent/Edge• Concentration• Motion, Mass/Volume Transport• Melt Onset, Length of Melt Season

• Age/Stage of Development• Thickness, thickness distribution• Snow Depth on Sea Ice• Leads and Polynyas• New Ice Formation (Brine Formation)

• Meltponds• Deformation• Ridges, Density/Height• Floe Size and Distribution• Brine Volume/Frost Flowers/Snow Grain

size• Chemistry and nutrient parameters (?)

• Icebergs

Larg

e-S

cale

Sm

all-

Sca

le

Radarsat, SAR

Current CapabilitiesSatellites

• Passive Microwave and Scatterometer, 10 – 50 km, daily– Large-scale extent, concentration, motion– Some info on ice age, edge– Snow depth (unvalidated)– Melt onset and freeze-up– Large iceberg tracking

• Visible/Infrared, 0.25 – 5 km, daily (limited by clouds)– Albedo, temperature– Thickness of thin ice– Some meltpond info (from high res.)– Medium to large iceberg tracking

• SAR, 0.1 – 0.5 km, 1-3 days– Motion, deformation, ridging, leads, new ice– Inference of FYI thickness– Can be difficult to interpret imagery– Surface roughness– Medium to large iceberg tracking

• Altimeter, 0.1 km, monthly composite, once per season– Sea ice and snow freeboard (laser), uncertainty converting to total thickness– Surface roughness – ridging, snow properties (?)– Medium to large iceberg height?

Current CapabilitiesSurface/Near-Surface

• Buoys, IABP and IBAP– Large-scale motion, met. conditions– 30-40 in Arctic, fewer in Antarctic– Mass balance buoys in Arctic (<10) – snow depth, internal/bottom temperatures,

fluxes• Surface ships

– Ice observations (ASPeCT standard, only applied in SH so far)• Submarine

– Historical thickness, no recent data– AUVs show promise for thickness

• Aircraft– Reconnaissance for ice edge/concentration– Iceberg tracking– UAVs for temperature, meltponds, leads, possibly thickness with altimeters

• Operational ice charts – integrate a variety of data sources for ice edge, concentration, age, thickness

– Weekly or bi-weekly– Effective spatial resolution and quality varies depends on quality/quantity of data

available

Operational vs. Climate• Operational needs best

possible information – new technologies can immediately be taken advantage of– Timeliness is key for products

• For climate records, consistency is more important than accuracy – tracking interannual variability and trends– Consistent algorithms, sensor

frequencies– Inter-sensor calibration is key– New technologies could be

used for improved reanalyses

Sea Ice Extent Climate Records

September Sea Ice Extent 1979 - 2006

5.00

5.50

6.00

6.50

7.00

7.50

8.00

8.50

9.00

19

79

19

81

19

83

19

85

19

87

19

89

19

91

19

93

19

95

19

97

19

99

20

01

20

03

20

05

Year

Ext

en

t, m

ill.

sq.

km.

NT GSFC

NIC

Hadley

PM Only

Fused/Operational(NIC charts,HadleyISST)

Sea Ice Extent Climate Records

September Arctic Ice Extent

5.00

5.50

6.00

6.50

7.00

7.50

8.00

8.50

1979

1981

1983

1985

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

Year

.Ex

ten

t ,m

ill

.sq

.k

m

NASA Team

Bootstrap

NASA Team Trend

Bootstrap Trend

Passive Microwave

Sea Ice Thickness• Altimeters providing first

dense basin-scale thickness coverage

• New technology, not proven for sea ice

• Uncertainties converting from freeboard to thickness (e.g., snow cover)

• Combining with SAR yields enhanced results (R. Kwok)

• Still limited temporal coverage (seasonal to annual), but enough?

• CryoSat-2 in 2009• ICESat-2?• Recovery of historical

records?

Lead

Parameter

CTO

Measurement RangeMeasurement Accuracy Resolution

Comment / Principal Driver

Spatial Temporal

L H U V U V U V U

Extent/Edge

CclCop

NA NA km150.1

km150.1

km13

day AMSR

T NA NA km 10 km 10 km 1 day CMIS

OclOop

NA NA km5

0.1km

1-50.1

km11

dayCMISSAR

Concentration

CclCop

0 100 % 5-20 % 15 km 1 dayAMSR, high summer

errors

T 0 100 % <10 % 15 km 1 day

O 0 100 % <5 % 10 km 1 day

Motion

CclCop

0 100 km day-1 50.5

km day-1 251

km13

dayAMSRSAR

T 0 100 km day-1 3 km day-1 25 km 1 day

OclOop

0 100 km day-1 10.5

km day-1 10.1

km11

dayMore frequent SAR

coverage

Thickness

CclCop

0 50 m0.510

m%

0.50.5

km0.51

yearweek

ICESatops ice charts

T 0 50 m

OclOop

0 50 m0.110

m%

250.5

km11

mnthday

sat. altimeter

Snow Depth on Ice

Ccl 0 100 cm 10-20 cm 15 km 1 day AMSR

T 0 100 cm 5 cm 10 km 1 day

Ocl 0 100 cm 2 cm 5 km 1 day

Parameter

CTO

Measurement RangeMeasurement Accuracy Resolution

Comment / Principal Driver

Spatial Temporal

L H U V U V U V U

Melt Onset, Duration of Melt

Ccl 1 365 jday 4 days 15 km 1 day AMSR

T 1 365 jday 2 days 15 km 1 day

Ocl 1 365 jday 1 day 10 km 1 day

Surface Albedo

Ccl 0 100 % 10 % 1 km 1 day

MODIS, but not currently produced

T 0 100 % 10 % 1 km 1 day

Ocl 0 100 % 1-5 % 0.5 km 1 day

Meltpond Coverage

Ccl 0 100 % 10 % 1 km 1 day

MODIS, but not fully developed

T 0 100 % 5 % 0.5 km 1 day

Ocl 0 100 % 5 % 0.1 km 1 day

Leads/polynyas

CclCop

00

100indet.

%km2

5-200.1

%km2

150.5

km11

dayweek

AMSRSAR

T

OclOop

00

100indet.

%km2

50.1

%km2

100.1

km11

day MODIS, PM

Volume/Mass Flux

Ccl

Currently no regular needed thickness est.T

Ocl 0 indet. km3 day-1 1km3 day-1 25 km 1 day

Priority Observations 1• Continued passive

microwave sensor [snow]– Consistent with current

sensors for trends– Algorithm evaluation and

development, fusion (of algorithms and with other sensor – e.g., scatterometer)

– Reanalysis to create CDR quality record, error estimates

– Biases in summer and thin ice regions

• Further development of altimeters for thickness [ice sheets]

• Continued SAR for operations, small-scale motion and deformation [ice sheets]

Monthly Mean Anomalies Normalized by Monthly 1979-2000 St. Deviation

-5

-4

-3

-2

-1

0

1

2

3

1979

1980

1982

1983

1985

1986

1988

1989

1990

1992

1993

1995

1996

1997

1999

2000

2002

2003

2005

2006

Year

# S

D f

rom

19

79

-20

00

Me

an

Monthly Mean

12-Month Running Mean

Arctic Sea Ice Extent

Priority Observations 2

• Continued support of buoys, including more mass balance buoys– Calibration/validation of

satellite/models

• Further development of autonomous surface and near-surface observations for calibration, validation, and small-scale variability– UAVs and AUVs– Buoys, esp. mass balance

• Visible/IR continuity – albedo, etc.

MODIS, Visible

Priority Activities• Passive microwave analysis/reanalysis [snow]• Resolve different algorithms, better intersensor calibration,

ground truthing for different surface types and spatial scales– Especially concentration, also motion, melt

• Solidify error estimates and error covariance [all]• Integration with models [all]

– Produce fields most useful to models, data assimilation• Data Fusion [all]

– e.g., active/passive microwave + vis/IR + SAR + altimeter + buoys + ???

• Develop reliable thickness/roughness products from satellite altimeters [ice sheets]

• Recover historical records and integrate with more recent records (e.g., observations from field expeditions, etc.) [all]

• Data documentation (metadata) and distribution, IPY-DIS to start? [all]

Outstanding Issues• Values in requirements table

need to be nailed down• Iceberg table very rough,

unsure of many values• What’s missing in text?

What in text is too much?– Operational vs. climate– Large-scale vs. small-scale

(how small?)• Cross-over with other

chapters• Integration with other

documents (GCOS)• Need images and image

suggestions• Where do ice shelves

belong?

SSM/I, Passive Microwave

Thanks!

Iceberg Capabilities and RequirementsParameter Horizontal

resolutionVerticalresolutio

n

Temporalresolution

Accuracy Latency Comments

Limit of IcebergArea

10 km - 12 hours 10% 2 hours Most important parameterto avoid icebergs

Concentrationof Icebergs

1 degree oflatitude andlongitude

- 12 hours 10% 2 hours Number of icebergs in agiven area – ship routePlanning

Position 1 km - 1 hour 10% 0.5 hour Collision avoidance

Size 1-10 m 1-10 m 24 hours 30% 2 hours Input to icebergdeterioration model;Iceberg towing (highest resolution)

Draft - 1-10 m 24 hours 30% 2 hours Input to iceberg driftmodel; Iceberg towing(highest res.)

Mass - - 24 hours 30% 2 hours Calculated

Drift Velocity 1 km/day - 24 hours 10% 2 hours Calculated