REGINA status update, 21 May 2015 Page 1

Regional glacial isostatic adjustment andCryoSat elevation rate corrections in Antarctica

(REGINA) – Supplementary StudyContract-Nr.: 4000107393/12/I-NB

REGINA Status Update 22 May 2015

STSE: CryoSat + Cryosphere

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Outline

• Characteristic of new data sets (altimetry & GPS) • 1st order GIA estimate (difference phase 1 and 2)• Impact of altimetry on GIA estimate

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Altimetry annual rates

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Cluster analysis of GPS

Raw data shown here →Symbol area inversely proportional to error.

Discrepant sites in a regionare often lower quality.

Weighted average of nearbysites will be minimallyaffected by low-quality data.

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Clustered GPS data

Iterative clustering of sitesup to 200 km separation.

No threshold for velocity diff.

Weighted mean of velocities,simple mean of site coordsin each cluster.

Far fewer regional discrepancies.

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GIA estimate (du/dt)

2003-2009

2003-2013

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GIA estimate (de/dt)

2003-2009 2003-2013

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Comparison: Phase 1 and Phase 2

Phase 1 Phase 2

2003-2009GRACEAltimetry

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dh/dt Amundsen Sea Embayment (ASE)

Phase 1 Phase 2

2003-2009

Phase 2

2003-2013

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Comparison: Phase 1 and Phase 2

Uniform errors of annual rates

Uniform density: 910 kg/m³

1st order GIA estimate: “GRACE minus altimetry”2003-2009

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Comparison: Phase 1 and Phase 2

1st order GIA estimate: “GRACE minus altimetry”

Non-uniform errors of dh/dt annual rates

Uniform density: 910 kg/m³

2003-2009

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Comparison: Phase 1 and Phase 2

1st order GIA estimate: “GRACE minus altimetry”

Uniform errors of dh/dt annual rates

Firn & density model applied

2003-2009

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Comparison: Phase 1 and Phase 2

1st order GIA estimate: “GRACE minus altimetry”

Uniform errors of dh/dt annual rates

Firn & density model applied

2003-2013

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Fully coupled 3D simulation

Ice model: Pollard & DeConto (2009)

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Discussion

Where do dh/dt differences come from?How can density model for Amundsen Sea Embayment be improved?What could be best way to constrain GIA estimate:• Introduction of a priori constraint on GIA / past loading• Force smoothness of recovered field?• A posteriori limitation of spectral range?Should 2010-2013 be included (CS2)?