H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

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, Austria2 Institute for Meteorology & Geophysics, Univ. Innsbruck3 DLR-IMF, Oberpfaffenhofen

H. 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 rise

H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

The main export of Antarctic ice is routed through ice shelves and lost by iceberg calving.

The Mass Balance of Grounded Ice is relevant for Sea Level Rise

Y

c dyyHyvB )()(

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 – BC

BC

Satellite observations provide key input for computing BC:

• The ice velocity at the cross section, v(y)• The surface elevation at the front (by altimetry, SAR)

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 thinning

H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

Retreat of Grounded Ice after Ice Shelf Collapse

Hektoria - Evans – Green Glacier

H. Rott, T. Nagler

Larsen IS, AAASAR

WSM 22 March 07

H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic PeninsulaH. Rott, T. Nagler

TerraSAR-X 28 March 2008

Deformation Pattern of Hektoria-Green-Evans Glaciers

H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

Mass fluxes for glaciers in Larsen-B embayment Drainage basins and calving gates

LandsatMarch 1986

H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

TerraSAR-X Data Set for Ice Velocities of Larsen Glaciers

70 Stripmap Scenes, June 2007 – Jan. 2010, 11-day repeat pass (multiple)

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- , ….. days

H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

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 glacier

Amplitude correlation for V

Ice Motion Retrieval – Example for Crane Glacier

ERS Tandem 1995/10/31-1995/11/01

1 day repeat pass – good coherence

H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

TerraSAR-X Crane Glacier, Oct. 2008 – Nov. 2009

H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

TerraSAR-X Velocity Profiles – Crane Glacier

P1 P2

Profiles for computing calving flux (P1) and dynamic thinning (P2, P1).

H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

Ice Thickness and Dynamic Thinning

h1

h2

w 1

w 2

v1

v2

P1

P2Surface lowering at P2 observed by ICESat

y

hv

x

hu

y

v

x

uhb

t

h

Flux divergence between 2 cross sections Surface lowering (mass continuity)

Cross section at P1, base extrapolated from bathymetry(Zgur et al., 2007)

2008

1999

H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

Glacier Gate Area

km2

Vc (m/yr) Discharge (Gt/yr)

1995/99 2008 1995/99 2008 Mass Deficit

Hektoria-

Green

H1,

G1

1091 387 1545 1.186 2.878 1.692 0.641

Evans E1 E2 210 93 474 0.144 0.459 0.315 0.099

Punchbowl PU1 102 65 183 0.058 0.155 0.097 0.034

Jorum N J2 56 68 146 0.042 0.082 0.040 0.019

Jorum S J1 318 475 865 0.346 0.534 0.188 0.131

Crane C1 1057 548 1882 1.149 2.919 1.770 0.614

Mapple MA1 165 46 82 0.061 0.109 0.048 0.026

Melville ME1 218 73 201 0.076 0.198 0.122 0.044

Pequod PE1 212 66 135 0.074 0.145 0.071 0.034

Sum   3327     3.136

0.537

7.479 1.542 4.343

1.642

Discharge of Glaciers in Larsen-B Embayment

H. Rott IGARSS 2011 Mass Deficit Glaciers Antarctic Peninsula

Glacier/Region Area [km²] 1999

Area [km²] 2003

Area [km²] 2004

Röhss Bay S-B Gl.

D-B-E Gl.

- 24 34

8 54 39

8 54 35

Gl. N. CW - 23 23 Drygalski Gl. 24 32 32

H-G-E Gl. - 57 41 Crane-JorumGl. - 3 22

Retreat of Grounded Ice since 1995 :

S-B Sjögren-BoydellD-B-E Dinsmoor-Bombardier-EdgeworthH-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)

Decrease in Ice Shelf Area Northern LIS 1995-2007

13 000 km2

Total 1995-2008

3567463335

11931

Glaciers of Northern LIS – Contribution to Sea Level Rise

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.