MONITORING THICKNESS CHANGES OF MOUNTAIN GLACIER BY DIFFERENTIAL

INTERFEROMETRY OF ALOS PALSAR DATA

Jianmin Zhou, Zhen Li, Qiang Xing

Key Laboratory of Digital Earth, Center for Earth Observation and Digital Earth, Chinese Academy of Sciences

2011.07.28 Vancouver

Outline

Research background

Study Area and Datasets

Methodology

Experimental Study

Conclusions

Future Work

• Important archives of past climatic information

• Important water source in dry areas (e.g. prairies)

• Indicators of climate fluctuations at local and global scale (IPCC)

• Important for climate change studies

• They contribute to sea level rise

Why study glacier?

Research background

Space-borne techniques have been developed and successfully applied for detecting glacier area change and glacier movement.

The major current gap in glacier monitoring from space lies in the measurement of glacier thickness or volume change for their contribution to sea-level change and as sensitive indicators of local climate.

Mass loss of mountain glaciers, ice caps and ice sheets are estimated to account for one third of the current 3 mm/yr of sea level rise( Cazenave, 2006, Science)

Monitoring the response of land ice to climate change requires accurate and multi-temporal topographic data.

Research background

Source: Dyurgerov and Meier 2005

Research background

Research backgroundProblems:

The current methodsTwo DEMS

Field GPS measurement

Lowprecision

costly andlaborious

DInSAR Monitoring technique: providing real-time deformation information avoiding costly and laborious with sparse

observing locations and unavailable in some inaccessible regions

DInSAR has demonstrated the capability of measuring displacement with mm accuracy over wide areas.

Not enough field measurements to do qualified validation, need of extra data

Study Area and DatasetsN

0 1km

This glacier belongs to a subcontinent high mountain glacier in low altitude. The accumulation season for this glacier starts from the end of spring and the beginning of summer and ends in the end of autumn. The ablation season is in the summer. Local circulation is weak and mass balance is controlled by Indian Ocean monsoon circulation in the Kangwure Glacier region. It was a flat-top glacier, inclining to northeast with flat surface, and there was no debris on the glacier surface.

Kangwure Glacier (28°27′N, 85°45′E) is situated on the north side of Mt. Xixiabangma, which is in the middle part of the Himalayas. The glacier terminus reaches to an altitude of 5680 m a.s.l. with an altitudinal difference of 476 m to the summit and the glacier exposes to the north in the upper area, then north-east.

Study Area and Datasets

Two winter ALOS/PALSAR orbits acquired on Jan. 21, 2010 and Mar. 8, 2010 with HH polarization covering Kangwure Glacier was exploited. The images were taken under favorable weather conditions and were selected in order to compute an interferogram with acquisition time intervals of 46 days and short baselines (132 m).

Datasets:

Acquisition Date Satellites Orbit type Seasons

2007-12-10 ALOS/PALSAR Ascending Winter

2008-01-25 ALOS/PALSAR Ascending Winter

A1

A2

r1

r2

Methodology INSAR GEOMETRY AND PHASE

PHASE CALCULATION

E 2 e j scatterere j

4 r2

E1 e j scatterere j

4 r1

E1E 2* e

j4 (r1 r2 )

or, simply, 4

(r1 r2)

Methodology

Methodology INSAR GEOMETRY - DEFORMATION

INSAR DEFORMATION PHASE

Phase similar to before but now has displacement term

To infer deformation, get difference and compensate for topo term, leaving only deformation signal in LOS direction.

2 1

4(def ) R

Methodology

Methodology

METHOD IN THIS STUDY

Methodology

InSARprocessing

InSAR pairs data (here, ALOS/PALSAR)

Glacier topography

Thickness changes of the glacier

Component decomposition

(a) The interferogram image at the Kangwure glacier area; (b): differential interferogram image at the Kangwure glacier area for ALOS/PALSAR pair between Jan. 21 and Mar. 8, 2010.

Experimental Study

High:3.464 cm

Low:-1.793 cm

N

0 1km

Thickness changes distribution map.

Experimental Study

Conclusions

In conclusion, the results imply that this method, compared to conventional method, has advantage to derive the glacier’s thickness changes in high-accuracy. According to the historical measurement data of the Kangwure glacier, our test study shows that the result is reasonable. The method developed in this study can be used to accurately extract glacier thickness changes.

Future Work

Need More InSAR Data

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