Thanks for the opportunity to get out of my NASA office
GRACE and GRACE Products Tutorial Jeanne Sauber, NASA Goddard Space Flight Center
J. Davis CIDER presentaFon, July 10, 2015
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Example satellite only, mean gravity field: -‐-‐GGMO5S, GRACE -‐-‐EIGEN-‐6S2 for GRACE Plo2er -‐-‐GOCO5S
Figure and capFon from hSp://earthobservatory.nasa.gov/Features/GRACE/page3.php
J. Davis CIDER presentaFon, July 10, 2015
Modified from J. Davis CIDER presentaFon, July 10, 2015
• Level 3 data of monthly surface mass changes of hydrologic, cryospheric, and oceanographic components.
KBR1B ex. Next slide
M 8.8 Maule Earthquake
Range-‐acceleraFon from individual satellite passes
Han, Sauber, Luthcke, GRL, 2011
Objec?ve: Contrast seismically derived early fault-‐slip models
Coseismic changes in range-‐rate March 11, 2011 Tohoku earthquake (M 9.2)
Han, Sauber, Riva, GRL, 2011
Interac(ve GRACE web site used in tutorial for visualizing solu(ons:
hSp://www.thegraceploSer.com/ DocumentaFon on “background” models for this site:
hSp://grgs.obs-‐mip.fr/grace
See JPL GRACE Tellus Project Web Site for links to different type soluFons & downloading data:
hSp://grace.jpl.nasa.gov/
hSp://podaac.jpl.nasa.gov/datasetlist?search=GRACE
NOTE: We start with the “Trend CNES” opFon with “water heights” Gravity funcFonal.
"Made with www.thegraceploSer.com, courtesy of CNES/GRGS"
# Linear model: Trend: -‐13.669 cm/year RMS of residuals (series-‐model): 19.193 cm
Periodic model: Least square adjustment: y=A+B(t-‐t0) +Ccos(ω(t-‐t0))+Dsin(ω(t-‐t0))+Ecos(2ω(t-‐t0))+Fsin(2ω(t-‐t0))
Annual amplitude: 22.14 cm
"Made with www.thegraceploSer.com, courtesy of CNES/GRGS"
Land ice mass evoluFon from GRACE
GSFC Mascon soluFon, Luthcke et al., J. of Glaciology, 2013 11
• 41,168 equal area 1-‐arc-‐degree mascons are directly esFmated from GRACE KBRR L1B data with spaFal and temporal exponenFal taper constraints applied.
• 10-‐day temporal resoluFon
• Spa(al constraint: 100 km correlaFon distance
• Temporal constraint: 10-‐day correlaFon
• Gulf of Alaska glacier region (61 mascons)
Gt Overall G of Alaska Trend = -‐69 ± 11 Gt a-‐1
Note variability in peak to peak seasonal amplitude and annual net balance (2005 versus 2012 balance year).
Gulf of Alaska
cm w.e.
Mascon 1484: North Central Smaller seasonal, 25-‐50 cm w.e. (peak to peak) Moderate 10-‐year trend
Mascon 1457: Central Coastal Moderate seasonal, 50-‐75 cm w.e., (peak to peak); Largest 10-‐year trend
Gt
Year
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Mascon 1425, South Eastern Alaska: Large seasonal: up to 100 cm w.e. (peak to peak) Large LiDle Ice Age PGR/GIA removed; Small 10 year-‐trend
SE
NC
Gulf of Alaska
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1425
1484
1457
CC
The differences in GRACE-‐derived seasonal changes are disFnct from region to region and from year to year.
GRACE MASCONS located adjacent or < 200 km to other mascons
1449
1457
1456
cm w.e.
Reminder: GRACE is sensi(ve to changes at spa(al scales > 300km
180 190 200 210 220 230 24040
45
50
55
60
65
70
75
80
−1
−0.5
0
0.5
1Postseismic gravity change in EWH [cm/yr]
Epicenter of the 1964 Alaska earthquake
~1 cm/yr
Simula?on of the present-‐day postseismic gravity change 1964 Mw = 9.2 Prince William Sound (Alaska) earthquake
-‐ Used Johnson et al. [1996] finite fault model: inversion of tsunami and geodeFc data to esFmate 1964 coseismic slip
-‐ We used the viscoelasFc Earth model that is consistent with other studies in this region [Suito and Freymueller, 2009; Sato et al., 2010]
-‐ Global normal mode relaxaFon code was used to compute the gravity change over the period 2002 -‐ 2014. (Courtesy of R. Riva and F. Pollitz)
=> ~1 cm/yr of gravity change (in w.e.) is predicted, primarily dependent on the asthenosphere viscosity (1019 Pa s)
Spherical harmonic coefficients from RL05 CSR L2 monthly data, degree up to 60; ~330 km resoluFon.
SchemaFc
Time-‐series at the epicenter (60N 212W)
2004 2006 2008 2010 2012 2014−80
−60
−40
−20
0
20
40
60
80
Year
Gra
vity
chan
ge in
EW
H [c
m]
GRACE RL05 L2 (CSR)Seasonal & secular fitSecular trend1964 EQ effect
GRACE secular trend ~ –8.3 cm/yr (observed RL05 CSR L2 ) 1964 EQ postseismic change ~ +1.0 cm/yr (model predicted)
The postseismic gravity change could be as large as 10% of the observed mass change, even 50 years a{er the 1964 earthquake.