I drift from ENVISAT ASAR WSM dataDanish National Space Center, DTU

Leif Toudal Pedersen & Roberto Saldo

Danish National Space Center

Technical University of Denmark

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Outline

• Method• Background – GMM mode images• NRT Ice drift from WSM images

• High resolution ice drift• Ice deformation

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• area of reference

• correlation area

• distance between vectors

• sampling

Method - Cross correlation

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Spatial resolution 35 km (GMM)

Temporal resolution (3-day – GMM)

GMM+WSM 3-day ice drift October 16-19, 2007

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Spatial resolution 35 km (GMM) or 10 km (WSM)

WSM 1-day ice drift October 18-19, 2007

Spatial resolution 10 km (WSM)

Temporal resolution (1-day – WSM)

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Accurate start and end time

• Drift is calculated from swath data– All swaths from day 0 is correlated with all swaths from day 1 (or day 3

for 3-day drift)

– Enables accurate start and end time contrary to using daily mosaics

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New DTU dataset available from June 1, 2007

• Daily drift vectors from all available ENVISAT ASAR WSM data • 1-day drift (12-36 hours)• 10 kilometer resolution (correlation of a circular area r=5km)• 10 kilometer grid (drift vector every 10 kilometers)• Arctic and Antarctic

• Examples: (Only daily average displacements are shown)

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Ice drift and deformation from SAR

• Application– Ice deformation (1-day, WSM, 3km resolution)

– The method is applied to WSM data fro the area north of Greenland– The 10 kilometer vectors are used as seed points– A new dataset of 3km resolution is derived (3km radius of correlation

area)– The ice drift field is differentiated and divergence is calculated

• Divergence corresponds to opening• Convergence corresponds to ridging

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Ice deformation

ENVISAT

ASAR

Sept 03

2007

Drift

Sept 2-3

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Ice deformation

ENVISAT

ASAR

Sept 2-3

2007

Divergence

September 2-3, 2007

Black is opening,

white is ridging

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Validation

• Validation with buoy data:

– RMS difference to AOBP buoy drifts 750m/day for the 1-day WSM drift at 10 kilometer resolution

• Movement of fast ice off East Greenland:– RMS: 80m/day for the high res ice motion (2000 obs)

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Ice drift and deformation from SAR

• Displacement NOT velocity – integrated quantity– In data assimilation: don’t assimilate velocities!

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Lincoln Sea 2007 animation

ENVISAT ASAR WSM animation by DTUDecember 27 (2006) to June 8 (2007)