Continental mass change from GRACE over 2002-2011 and its ... · CSR, release 04 (temporal...
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GGHS 2012 Venice | Italy | 9–12 October 2012 Continental mass change from GRACE over 2002-2011 and its impact on sea level Oliver Baur 1 , Michel Kuhn 2 , Will Featherstone 2 1 Space Research Institute, Austrian Academy of Sciences, Graz 2 Western Australian Centre for Geodesy, Curtin University of Technology, Perth
Transcript of Continental mass change from GRACE over 2002-2011 and its ... · CSR, release 04 (temporal...
GGHS 2012Venice | Italy | 9–12 October 2012
Continental mass changefrom GRACE over 2002-2011and its impact on sea level
Oliver Baur1, Michel Kuhn2, Will Featherstone2
1Space Research Institute, Austrian Academy of Sciences, Graz2Western Australian Centre for Geodesy, Curtin University of Technology, Perth
Outline
Methods
Results
Conclusions
Methods
Mass-change trends from GRACE
Period of investigationGravity fields“Manipulation”
Degree-1 termsc20 coefficients
Post-processingDe-correlationSpatial averaging
Inference of mass variationSurface mass-densitiesLeakage consideration
Signal separationGIA model
Time-series fit
May 2002 to April 2011 (9 integer years)CSR, release 04 (temporal resolution ≈1 month)
SLR-derived geocenter coordinates (taken from CSR)replaced by results from SLR (taken from CSR)
according to Swenson and Wahr (2006)Gaussian smoothing with a radius of 500 km
according to Wahr et al. (1998)according to Baur et al. (2009)
according to Paulson et al. (2007)linear trend function together with four sinusoids
Methods
Mass-change trends from GRACE
Period of investigationGravity fields“Manipulation”
Degree-1 termsc20 coefficients
Post-processingDe-correlationSpatial averaging
Inference of mass variationSurface mass-densitiesLeakage consideration
Signal separationGIA model
Time-series fit
May 2002 to April 2011 (9 integer years)CSR, release 04 (temporal resolution ≈1 month)
SLR-derived geocenter coordinates (taken from CSR)replaced by results from SLR (taken from CSR)
according to Swenson and Wahr (2006)Gaussian smoothing with a radius of 500 km
according to Wahr et al. (1998)according to Baur et al. (2009)
according to Paulson et al. (2007)linear trend function together with four sinusoids
Methods
Mass-change trends from GRACE
Period of investigationGravity fields“Manipulation”
Degree-1 termsc20 coefficients
Post-processingDe-correlationSpatial averaging
Inference of mass variationSurface mass-densitiesLeakage consideration
Signal separationGIA model
Time-series fit
May 2002 to April 2011 (9 integer years)CSR, release 04 (temporal resolution ≈1 month)
SLR-derived geocenter coordinates (taken from CSR)replaced by results from SLR (taken from CSR)
according to Swenson and Wahr (2006)Gaussian smoothing with a radius of 500 km
according to Wahr et al. (1998)according to Baur et al. (2009)
according to Paulson et al. (2007)linear trend function together with four sinusoids
Degree-1 terms (geocenter motion)
Methods
Degree-1 terms (geocenter motion)
Methods
Geocenter motion correction implies mass loss in the Northern Hemisphere and mass gain in the Southern Hemisphere
Geocenter motion estimates have large error bounds
Questionable reliability of secular trends in SLR-derived geocentercoordinates: two-track processing scheme
Methods
Mass-change trends from GRACE
Period of investigationGravity fields“Manipulation”
Degree-1 termsc20 coefficients
Post-processingDe-correlationSpatial averaging
Inference of mass variationSurface mass-densitiesLeakage consideration
Signal separationGIA model
Time-series fit
May 2002 to April 2011 (9 integer years)CSR, release 04 (temporal resolution ≈1 month)
SLR-derived geocenter coordinates (taken from CSR)replaced by results from SLR (taken from CSR)
according to Swenson and Wahr (2006)Gaussian smoothing with a radius of 500 km
according to Wahr et al. (1998)according to Baur et al. (2009)
according to Paulson et al. (2007)linear trend function together with four sinusoids
Methods
Mass-change trends from GRACE
Period of investigationGravity fields“Manipulation”
Degree-1 termsc20 coefficients
Post-processingDe-correlationSpatial averaging
Inference of mass variationSurface mass-densitiesLeakage consideration
Signal separationGIA model
Time-series fit
May 2002 to April 2011 (9 integer years)CSR, release 04 (temporal resolution ≈1 month)
SLR-derived geocenter coordinates (taken from CSR)replaced by results from SLR (taken from CSR)
according to Swenson and Wahr (2006)Gaussian smoothing with a radius of 500 km
according to Wahr et al. (1998)according to Baur et al. (2009)
according to Paulson et al. (2007)linear trend function together with four sinusoids
Methods
Mass-change trends from GRACE
Period of investigationGravity fields“Manipulation”
Degree-1 termsc20 coefficients
Post-processingDe-correlationSpatial averaging
Inference of mass variationSurface mass-densitiesLeakage consideration
Signal separationGIA model
Time-series fit
May 2002 to April 2011 (9 integer years)CSR, release 04 (temporal resolution ≈1 month)
SLR-derived geocenter coordinates (taken from CSR)replaced by results from SLR (taken from CSR)
according to Swenson and Wahr (2006)Gaussian smoothing with a radius of 500 km
according to Wahr et al. (1998)according to Baur et al. (2009)
according to Paulson et al. (2007)linear trend function together with four sinusoids
Methods
Mass-change trends from GRACE
Period of investigationGravity fields“Manipulation”
Degree-1 termsc20 coefficients
Post-processingDe-correlationSpatial averaging
Inference of mass variationSurface mass-densitiesLeakage consideration
Signal separationGIA model
Time-series fit
May 2002 to April 2011 (9 integer years)CSR, release 04 (temporal resolution ≈1 month)
SLR-derived geocenter coordinates (taken from CSR)replaced by results from SLR (taken from CSR)
according to Swenson and Wahr (2006)Gaussian smoothing with a radius of 500 km
according to Wahr et al. (1998)according to Baur et al. (2009)
according to Paulson et al. (2007)linear trend function together with four sinusoids
Leakage consideration
Methods
Leakage consideration
Methods
Methods
Mass-change trends from GRACE
Period of investigationGravity fields“Manipulation”
Degree-1 termsc20 coefficients
Post-processingDe-correlationSpatial averaging
Inference of mass variationSurface mass-densitiesLeakage consideration
Signal separationGIA model
Time-series fit
May 2002 to April 2011 (9 integer years)CSR, release 04 (temporal resolution ≈1 month)
SLR-derived geocenter coordinates (taken from CSR)replaced by results from SLR (taken from CSR)
according to Swenson and Wahr (2006)Gaussian smoothing with a radius of 500 km
according to Wahr et al. (1998)according to Baur et al. (2009)
according to Paulson et al. (2007)linear trend function together with four sinusoids
GIA model
Methods
GIA models are subject to large error bounds (particularly over Antarctica)
Adopted uncertainty level: 30%
Methods
Mass-change trends from GRACE
Period of investigationGravity fields“Manipulation”
Degree-1 termsc20 coefficients
Post-processingDe-correlationSpatial averaging
Inference of mass variationSurface mass-densitiesLeakage consideration
Signal separationGIA model
Time-series fit
May 2002 to April 2011 (9 integer years)CSR, release 04 (temporal resolution ≈1 month)
SLR-derived geocenter coordinates (taken from CSR)replaced by results from SLR (taken from CSR)
according to Swenson and Wahr (2006)Gaussian smoothing with a radius of 500 km
according to Wahr et al. (1998)according to Baur et al. (2009)
according to Paulson et al. (2007)linear trend function together with four sinusoids
Time-series fit
Greenland Amazon basin
Methods
Trend function + annual and semi-annual signals + S2 and K2 tidal aliases
Adoption of linear vs. quadratic trend model of secondary importance
Results – regional balance
Regions of interest
Region selection according to continental areas with dominant GRACE signal
Different delineations are compensated equally during the leakage-correction procedure
Separation between physically meaningful signals and GRACE errors/artefacts
Trade-off: continental regions with signal amplitudes stronger than the strongest signal magnitude over the world’s oceans
Artefacts may be interpreted as meaningful signals and vice versa
Continental signals outside the regions of interest balance close to zero
Regions of interest
Results – regional balance
Regiongeocenter
neglected corrected
1 Greenlanda -286±15 -323±26
2 West Antarctica -201±40 -169±46
3 Alaska -47±5 -56±7
4 Parana -27±6 -26±7
5 Euphrates/Tigris -25±5 -27±6
6 Brahmap./Ganges -24±4 -25±6
7 Volga -24±5 -28±6
8 Patagonia -12±2 -10±3
9 West Australia -9±2 -7±3
Regiongeocenter
neglected corrected
10 East Antarctica 51±10 65±13
11 Amazon 50±13 43±14
12 Zambezi/Okavango 38±7 40±8
13 Canada 51±110 25±111
14 Fennoscandia 18±23 12±23
15 Central Siberia 13±2 10±4
16 East Australia 12±3 14±3
17 Niger 9±2 8±2
18 Kamchatka 9±2 6±3
19 Godavari/Krishna 3±1 4±1
aIncluding Iceland, Svalbard and the Canadian Arctic archipelagoUncertainties are given at the 95% (2σ) confidence level
Regions of interest – mass-change trends [Gt/yr]
Results – regional balance
Zambezi/Okavango mass-change trend [Gt/yr]
This study 05/2002–04/2011: 40 ± 8
Llovel et al. (2010) 08/2002–07/2009: 21 ± 3
Re-computation 08/2002–07/2009: 27 ± 12
Subset period: 3 yearsSubset shift: 36 monthsSubset period: 5 yearsSubset shift: 6 months
Comparison with other studies …a serious pitfall
Amazon basin mass-change trend [Gt/yr]
This study 05/2002–04/2011: 43 ± 14
Llovel et al. (2010) 08/2002–07/2009: 78 ± 9
Re-computation 08/2002–07/2009: 71 ± 19
Amazon basin mass-change trend [Gt/yr]
This study 05/2002–04/2011: 43 ± 14
Llovel et al. (2010) 08/2002–07/2009: 78 ± 9
Comparison with other studies
Results – regional balance
Sea-level change equivalent [mm/yr]
Translation of mass gain or mass loss over land areas into homogeneouswater changes over the world’s oceans
geocenter
neglected corrected
Sea-level rise 1.8±0.2 1.9±0.2
(Glaciated areasa 1.4±0.2 1.4±0.2)
Sea-level fall -0.7±0.4 -0.6±0.4
Balance 1.1±0.6 1.2±0.6aGreenland (incl. Iceland, Svalbard, Canadian Arctic archipelago), Antarctica, Alaska and PatagoniaUncertainties are given at the 95% (2σ) confidence level
Land-water mass accumulation compensates about 20% of the impact of ice-melt water influx to the oceans
Geocenter motion affects sea level rise and sea level fall estimates equally; the net effect is 0.1±0.1 mm/yr
Results – global balance
Study Period Land-ice Land-water Total
Llovel et al. (2010) 08/2002-07/2009 - -0.2±0.1 -
Jacob et al.(2012) 01/2003-12/2010 1.5±0.3 - -
Riva et al. (2010) 02/2003-02/2009 1.0±0.2a -0.1±0.3 1.0±0.4
This study 05/2002-04/ 2011 1.4±0.2a -0.1±0.3 1.2±0.6
Comparison with other studies (rates are in [mm/yr])
aGreenland (incl. Iceland, Svalbard, Canadian Arctic archipelago), Antarctica, Alaska and PatagoniaUncertainties are given at the 95% (2σ) confidence level
Continental mass change
Study Period Total
Lombard et al. (2007) 2002-2006 1.2±0.5
Leuliette and Willis (2011) 01/2005-09/2010 1.1±0.6
Results – global balance
Ocean mass trend
Conclusions
First study that selects the regions of interest exclusively on the basis of dominant GRACE signal (no a priori spatial information)
Isolation and quantification of individual contributions to the global budget
The integrated mass change within the selected regions is representative for the variation over the whole land area
It remains an open issue whether the overall sea-level change budget is closed
The computation of mass variation from GRACE has been becoming increasingly heterogeneous; “conventions” would improve consistency
Baur O., Kuhn M., Featherstone W. (2012) Continental mass change from GRACE over 2002-2011 and its impact on sea level, Journal of Geodesy, online first
