IGARSS11_TH2.T04.3_Rott_Larsen.ppt

Mass Deficit of Glaciers at the Northern Antarctic Peninsula derived from Satellite- borne SAR and Altimeter Measurements Helmut Rott1,2, Florian Müller1, Thomas Nagler1 Dana Floricioiu3, Michael Eineder3 1 ENVEO IT GmbH, Innsbruck, Austria 2 Institute for Meteorology & Geophysics, Univ. Innsbruck 3 DLR-IMF, OberpfaffenhofenH. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

Contents of Presentation • The Scientific Question: Glacier contributions to sea level rise after ice shelf disintegration • Data sources and method • Overview on Collapse of Larsen-A and-B Ice Shelf • Example for acceleration of glaciers after collapse: Crane Glacier • Dynamic thinning by ICESat altimetry and mass continuity • The contribution to sea level riseH. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

The Mass Balance of Grounded Ice is relevant for Sea Level Rise The main export of Antarctic ice is routed through ice shelves and lost by iceberg calving. BC The contribution to sea level rise is determined by the imbalance of net accumulation, BA, on grounded ice minus the export through a cross section at the grounding line or calving front, BC: BN = BA – BCSatellite observations provide key input for computing BC:• The ice velocity at the cross section, v(y) Bc v ( y) H ( y) dy• The surface elevation at the front (by altimetry, SAR) Y enabling to estimate ice thickness H H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

Investigation of Mass Imbalance of Glaciers• The Question: The response and mass imbalance of glaciers after disintegration of northern LIS: Prince Gustav Channel (PCG), Larsen-A, Larsen-B• Data sources: Precise maps of ice velocity for all glaciers: - Pre-collapse ERS-1/ERS-2 tandem interferometry (1day repeat) 1995-99 - TerraSAR-X (2m res.) incoherent amplitude correlation 2007-2010 ICESat profiles (repeat pass) near grounding line for a few glaciers Ice thickness of Crane Glacier: Bathymetry in fjord and airborne sounder (CReSIS, Univ. Kansas) 2002, 2004, 2009, 2010 (ambiguous signals) Bathymetry in front of Crane Glacier 2006 (Zgur et al.) Approach: Compute fluxes across gate near 2008 ice front Pre-collapse state of glaciers close to balance V(1999) = V(1995) Pre-collapse net balance from flux Fy (1995,1999) Post-collapse Fy refers to 2008-09, taking into account thinningH. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

Retreat of Grounded Ice after Ice Shelf Collapse Hektoria - Evans – Green Glacier Larsen IS, AA ASAR WSM 22 March 07H. Rott, T. Nagler H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

Deformation Pattern of Hektoria-Green-Evans Glaciers TerraSAR-X 28 March 2008H. Rott, T. Nagler H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

Mass fluxes forglaciers in Larsen-BembaymentDrainage basins andcalving gatesLandsatMarch 1986H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

TerraSAR-X Data Set for Ice Velocities of Larsen Glaciers Method: Motion mapping by incoherent amplitude correlation • Provides 2 components of velocity Vector • Requires persistent features • Does not require coherence • Accuracy < 5 cm/day (with 11- day repeat pass) • Apply multiple pairs: 11-, 22-, 33- , ….. days70 Stripmap Scenes, June 2007 – Jan. 2010, 11-day repeat pass (multiple)H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

Ice Motion Retrieval – Example for Crane Glacier Frontal Velocity 1995 1.7 m/d ERS InSAR 2007 7.2 m/d TerraSAR-X TerraSAR-X 18-29/10/2008 Decorrelates on fast glacierERS Tandem 1995/10/31-1995/11/01 Amplitude correlation for V1 day repeat pass – good coherence H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

TerraSAR-X Crane Glacier,H. Rott IGARSS 2011 Oct. 2008 – Nov. 2009 Mass Deficit Glaciers Antarctic Peninsula

TerraSAR-X Velocity Profiles – Crane Glacier P1 P2Profiles for computing calving flux (P1) and dynamic thinning (P2, P1).H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

Ice Thickness and Dynamic Thinning v1 h1 w1 P1 v2 h2Surface lowering at P2 observed by ICESat P2 w2 Flux divergence between 2 cross 2008 sections Surface lowering (mass continuity) 1999 h u v h h b h u v t x y x yCross section at P1, base extrapolated frombathymetry(Zgur et al., 2007) H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

Discharge of Glaciers in Larsen-B EmbaymentGlacier Gate Area Vc (m/yr) Discharge (Gt/yr) km2 1995/99 2008 1995/99 2008 Mass DeficitHektoria- H1, 1091 387 1545 1.186 2.878 1.692 0.641Green G1Evans E1 E2 210 93 474 0.144 0.459 0.315 0.099Punchbowl PU1 102 65 183 0.058 0.155 0.097 0.034Jorum N J2 56 68 146 0.042 0.082 0.040 0.019Jorum S J1 318 475 865 0.346 0.534 0.188 0.131Crane C1 1057 548 1882 1.149 2.919 1.770 0.614Mapple MA1 165 46 82 0.061 0.109 0.048 0.026Melville ME1 218 73 201 0.076 0.198 0.122 0.044Pequod PE1 212 66 135 0.074 0.145 0.071 0.034Sum 3327 3.136 7.479 4.343 0.537 1.542 1.642H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

Glaciers of Northern LIS – Contribution to Sea Level Rise Retreat of Grounded Ice since 1995 Total :Glacier/Region Area [km²] Area [km²] Area [km²] 1995- Decrease in Ice Shelf 1999 2003 2004 2008 Area Northern LIS Röhss Bay - 8 8 35 1995-2007 S-B Gl. 24 54 54 67 13 000 km2 D-B-E Gl. 34 39 35 46 Gl. N. CW - 23 23 33 Drygalski Gl. 24 32 32 35 S-B Sjögren-Boydell H-G-E Gl. - 57 41 119 D-B-E Dinsmoor-Bombardier-EdgeworthCrane-JorumGl. - 3 22 31 H-G-E Hektoria-Green-Evans Total Retreat of Grounded Ice Area 1995 -2008: 360 km2 Retreat of Grounded Ice March 2002 to 2008: 250 km² g 0.06 mm SLE (sea level equivalent, assuming 80 m height above buoyancy) Sea level equivalent contribution due to export at glacier fronts 2002 – 2008, Larsen A and B: 0.03 mm/a. Total SLE (2002-2008) 0.04 0.01 mm/a (ca. 3% of eustatic SLR) H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

• The rapid disintegration of Northern Larsen Ice Shelf demonstrates the high sensitivity of polar ice masses to climate change – the retreat proceeding faster than predicted by models.• Repeat-pass SAR data offer unique capabilities to study flow dynamics of glaciers and ice streams with great detail. In synergy with precise surface topography (altimetry, TanDEM-X) mass balance can be retrieved.• The sea level contribution of the glaciers above Larsen-A and -B is not very significant, but the studies are important for predicting the dynamic response of large ice masses if warming spreads further south. H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

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