STSE Cryo Sat Cryosphere Study Regional glacial isostatic

STSE Cryo. Sat+ Cryosphere Study Regional glacial isostatic adjustment and Cryo. Sat elevation rate corrections in Antarctica Ingo Sasgen& REGINA consortium (REGINA) www. regina-science. eu (Mark Drinkwater, ESA); Contract-Nr. : 4000107393/12/I-NB V. Klemann, L. Petrie, P. Clarke, N. Schön, Contact: sasgen@gfz-potsdam. de J. L. Bamber, R. Pail, M. Horwath, A. Horvath REGINA (www. regina-science. eu): Ingo Sasgen (PI), Martin Horwath, Volker Klemann, Elizabeth J. Petrie, Nana Schoen, Roland Pail, Alexander Horvath, Jonathan L. Bamber, Peter J. Clarke, Hannes Konrad and Mark R. Drinkwater (ESA) ESA Cli. C workshop, Tromsø, 20 January 2015 Page 1

Glacial-isostatic adjustment ESA Cli. C workshop, Tromsø, 20 January 2015 Page 2

Flow-line GIA simulation, example Shelf Ice sheet Ocean Bedrock Glacial-isostatic adjustment (GIA) [1] Hannes Konrad, Ingo Sasgen, Volker Klemann (GFZ) ESA Cli. C workshop, Tromsø, 20 January 2015 Page 3

Approaching GIA in Antarctica Earth observation GPS, GRACE, Altimetry Numerical modelling Earth / Ice models, Paleo observations etc. REGINA aims: • Determine GIA elevation rate correction for Cryo. Sat-2 • Investigate Crustal Low Viscosity Zone • Employ multiple space-geodetic data sets GIA prediction e. g. Whitehouse et al. 2012 Ivins & James 2005 (“IMBIE-models”) Hybrid GIA estimate Sasgen et al. 2013 GIA estimate e. g. Riva et al. 2009, Gunter et al. 2014 ESA Cli. C workshop, Tromsø, 20 January 2015 Page 4

Present and past ice-mass change Deglaciation since LGM Accumulation event ESA Cli. C workshop, Tromsø, 20 January 2015 Page 5

Observation equations • System of linear equations Satellite observations Earth response Elastic Viscous Consideration of Earth structures & Filtering GRACE Present mass change Past mass change GPS Compaction (density ch. ) ICESat/Env. Solution with discs on geodesic grid Reprocessed data Kernels*: Ice-elevation change Gravitational potential Bedrock displacement * Filtered according to observation ESA Cli. C workshop, Tromsø, 20 January 2015 Page 6

Altimetry ICESat / Envisat combination for 2003 -2009 [1] Combination mask ICESat available only ICESat (smaller errors) Envisat (smaller errors) N. Schön, J. Bamber, Univ. Bristol 10 km gridded data ESA Cli. C workshop, Tromsø, 20 January 2015 Page 7

Gravimetry A. Horvath, R. Pail (TU München), M. Horwath (TU Dresden) ESA Cli. C workshop, Tromsø, 20 January 2015 Page 8

GPS displacements Review of metadata Test of processing options Trend estimation accounting for colored noise available unavailable partially available [1] L. Petrie (now Univ. Glasgow), P. Clarke (Newcastle Univ. ) ESA Cli. C workshop, Tromsø, 20 January 2015 Page 9

Geometrical set-up Spatial distribution of discs 1175 discs Shear velocity anomalies[1] with respect to PREM[2] East Ant. Rheology (200 km Elast. lith. ) West Ant. Rheology (variable) Deviation (%) Earth structure dependent response kernels[3] [1] Danesi & Morelli (2001); [2] Dziewonski & Anderson (1981) Possibility: GOCE constraints [3] V. Klemann, I. Sasgen (GFZ) ESA Cli. C workshop, Tromsø, 20 January 2015 Page 10

Step 1: first-order GIA estimate Removal of surface-mass contributions Different scale GRACE [1] Altimetry [1] = [1] Post-processing I: Swenson & Wahr, 2006 + Gaussian 200 km (GFZ RL 05) ESA Cli. C workshop, Tromsø, 20 January 2015 Page 11

GIA estimate for Antarctica ESA Cli. C workshop, Tromsø, 20 January 2015 Page 12

Influence of Earth structure Weak Strong IMBIE Weak+Filtering ESA Cli. C workshop, Tromsø, 20 January 2015 Page 13

Separation of ice mass and GIA Ice-mass balance 2003 -2009 GIA estimate ESA Cli. C workshop, Tromsø, 20 January 2015 Page 14

GIA apparent mass change (selection) But again: spread GIA corrections > GRACE signal ESA Cli. C workshop, Tromsø, 20 January 2015 REGINA 2003 -2008: -63 to -75 Gt/yr (IMBIE: -72 Gt/yr) Page 15

IOM validation of REGINA estimates IOM [1] mass balance: − 66 Gt/yr (c. f. Rignot, IOM-IMBIE: − 142 Gt/yr) REGINA mass balance: − 63 to -75 Gt/yr (Envisat/ICESat & GRACE combination) [1] Depoorter, M. A. , J. L. Bamber, J. A. Griggs, J. T. M. Lenaerts, S. R. M. Ligtenberg, M. R. van den Broeke, and G. Moholdt (2013), Calving fluxes and basal melt rates of Antarctic ice shelves, Nature, 502(7469), 89 -92. ESA Cli. C workshop, Tromsø, 20 January 2015 Page 16

REGINA Phase 1 conclusions • Combination algorithm ü Includes GRACE, Envisat/ICESat, GPS ü Accounts for different filtering / resolutions ü Solves for local density changes (no a priori model req. ) • Refined Earth structure considers ü Crustal low-viscosity zone ü East and West Antarctic rheology ü Low mantle viscosities (beyond IMBIE range; not shown) • Results ü GIA apparent mass change of 26 to 38 Gt/yr ü Ice-mass balance of − 63 to − 75 Gt/yr (IMBIE – 72 Gt/yr) • Next steps: final GIA product in REGINA Phase 2 (08/2015) ESA Cli. C workshop, Tromsø, 20 January 2015 Page 17

www. regina-science. eu ESA Cli. C workshop, Tromsø, 20 January 2015 Page 18

Apparent mass change of GIA IMBIE (not used) IMBIE (used) GIA correction ICE-5 G IJ 05_R 2 W 12 a Type Numerical prediction Data set used Geomorphology, Paleoclimate, Geomorphology, relative sea-level Paleoclimate data (GIA) Numerical prediction Ice-dynamics, Paleoclimate, geomorphology, relative sea-level data (GIA) Spatial resolution 256 (SH degree) provided Earth model Yes (implicit) Yes assumptions Sasgen et al. Ivins et al. 2013; Reference doi: 10. 1002/jgrb. 50 doi: 10. 5194/tcd-6 208 -3703 -2012 Apparent mass change (Gt/yr) 140 to 180 40 to 65 Post IMBIE AGE 1 REGINA ICE-6 G IJ 05_R 2_5 k Geodetic estimate Numerical prediction GPS, GIA ensemble modelling ICESat/Envisa Geomorphology, t, GRACE, Paleoclimate, GPS, GIA relative sea-level kernels data (GIA) Geomorphology, Paleoclimate 60 120 96 - 256 Yes No No Yes (implicit) Yes Whitehouse et al. Sasgen et al. 2013; 2012 b; www. reginadoi: 10. 5194/tcd-6 doi: 10. 1111/j. 1365 science. eu -3703 -2012 246 X. 2012. 05557. x ca. 60 49 Argus et al. 2014; Velicogna et al. doi: AGU 2014, 10. 1093/gji/ggu 14 G 51 A-0343 0 26 to 38 107 ca. 120 GRACE minus REGINA GIA, 2003 -2008 -63 to -75 Gt/yr (IMBIE: -72 Gt/yr) GRACE minus REGINA GIA, 2003 -2014 -100 to -112 Gt/yr ESA Cli. C workshop, Tromsø, 20 January 2015 Page 19

Data availability Additional signals CSR RL 05 ICESat CSR RL 05 @ ICESat Too noisy for GRACE CSR RL 05 & ICESat [selected] Best ESA Cli. C workshop, Tromsø, 20 January 2015 Page 20

Geoid rate (e’) to disc load Load + Elastic response Load + viscoelastic response Jmax=2048 (Model) hl=90 km (thick) µAst. = 1 1018 Pa s (weak) Relaxation, without load Each line: response after +Δt = 10 yrs; Sim. period: 2 kyrs ESA Cli. C workshop, Tromsø, 20 January 2015 Page 21

Displacement rate (u’) to disc load Load dimension Elastic response hl=90 km (thick) Viscoelastic response Relaxation, without loading µAst. = 1 1018 Pa s (weak) Each line: response after +Δt = 10 yrs; Sim. period: 2 kyrs ESA Cli. C workshop, Tromsø, 20 January 2015 Page 22

Separation ice-mass and GIA (geoid) Present-day ice-mass change Filter 2: Statistical filter + Wiener filter Filter 1: REGINA GIA ESA Cli. C workshop, Tromsø, 20 January 2015 Page 23

Radial displacement rate for disc load “standard” West Antarctica “weak” West Antarctica Mention paper: GOCE (strong) 30 km 90 km 3 x 1019 Pa s (stiff) • Weaker lithosphere more localized & greater amplitudes • Viscosity not important within REGINA context (weak) 3 x 1019 Pa s (stiff) V. Klemann, I. Sasgen, GFZ ESA Cli. C workshop, Tromsø, 20 January 2015 Page 24

Procedure of separation ESA Cli. C workshop, Tromsø, 20 January 2015 Page 25

Step 2: Refinement with GPS ESA Cli. C workshop, Tromsø, 20 January 2015 Page 26

Step 2: Refinement with GPS West Ant. rheol. Jmax=2048 Elastic response (present loading) East Ant. rheol. Viscous response (past loading) Elastic response (present loading) ESA Cli. C workshop, Tromsø, 20 January 2015 Jmax= 90 & 200 km Gaussian Page 27

GRACE e’ vs. GPS u’ (Altim. removed) West Ant. rheol. ESA Cli. C workshop, Tromsø, 20 January 2015 East Ant. rheol. Page 28

Elastic and viscoelastic kernels Axisymmetric disc load: 62 km radius, mass gain 5. 6 Gt/yr Lo ad rat ec on sta nt Temporal evolution Radius constant Jmax=2048 ~ 10 km V. Klemann, I. Sasgen, GFZ Viscoelastic Earth model: Martinec, 2000 ESA Cli. C workshop, Tromsø, 20 January 2015 Page 29