Remote sensing estimates of glacier mass balances in the Himachal Pradesh (Western Himalaya, India)

TLDR: In this article, the authors used remote sensing data to monitor glacier elevation changes and mass balances in the Spiti/Lahaul region (32.2°N, 77.6°E, Himachal Pradesh, Western Himalaya, India).

About: This article is published in Remote Sensing of Environment.The article was published on 2007-06-15 and is currently open access. It has received 503 citations till now. The article focuses on the topics: Glacier mass balance & Glacier.

Figures

Table 1: Characteristics of the SPOT5 and ASTER images used in this study.

Figure 2: Synthetic perspective view of the Bara Shigri (left panel) and Chhota Shigri (right panel) glaciers obtained by draping a SPOT5 image ov r a DEM. No vertical exaggeration. Note the rough surface of the debris-covered tongue of Bara Shigri and the occurrence of fresh snow on the slopes surrounding the glaciers.

Figure 5: Estimate of the planimetric shift between the two DEMs. The method is illustrated first using a profile on the two upper panels and then applied to the real case on the lower panel. (a) Comparison of SRTM and SPOT5 elevations along a profile in a non-glaciarized area. (b) The SPOT5 profile shown in the upper panel is shifted by fractions (0.5) of pixel. For each value of this shift, the mean difference {SPOT5-SRTM} and standard deviation of this difference is given. (c) Contour plot of the standard deviation of the difference {SPOT5-SRTM} for different value of shifts in latitude and longitude. The minimum in this contour plot indicates the mean horizontal shift between the two DEMs.

Figure 9: The glacier inventory for the Spiti/Lahaul region. Nearly 915 km2 of glaciers have been delimited from an ASTER image acquired in September 2002.

Table 3: Total area and specific mass balances between 1999 and 2004 as a function of glacier size. A designs the area of each individual glacier ; ΣA the cumulated area for each sample ; N the number of glaciers in each sample ; b1 and b2 the specific mass balances computed using, respectively, hypothesis 1 and 2 described in the main text (section 4.3).

Figure 8: Biases between SRTM and the SPOT5 DEMs as a function of altitude on the ice free areas. The values of the linear biases with altitude are indicated in two cases. Alt Bias1 takes into account all the points whereas Alt Bias2 excludes th two extreme points.

Frequently asked questions

Q1. What have the authors contributed in "Remote sensing estimates of glacier mass balances in the himachal pradesh (western himalaya, india)" ?

In this paper, the authors used remote sensing data to monitor glacier elevation changes and mass balances in the Spiti/Lahaul region ( 32.2°N, 77.6°E, Western Himalaya, India ). 

Q2. What is the importance of monitoring glaciers in the Himalayas?

Monitoring their evolution is a key issue as the melting of all glaciers in central Asia may significantly contribute to ongoing sea level rise (Kaser et al., 2006). 

Q3. How many well-distributed GCPs are generated for each image?

A set of about 100 well-distributed GCPs is then generated automatically for each image by using the stereo model of the reference SPOT5 image, the improved stereo model of the secondary image and SRTM elevations. 

Q4. What can be done to correct the biases between the two DEMs?

After the biases between the two DEMs have been identified and corrected, glacial elevation changes can be computed and analyzed. 

Q5. What is the overall specific mass balance for the Chhota Shigri glacier?

The overall specific mass balance is -0.7 to -0.8 m/a w.e., showing that glaciers of the Spiti/Lahaul region are experiencing rapid ice losses. 

Q6. How many uncertainties can lead to a shifted SPOT5-DEM?

The uncertainties (+/- 25 m) in the geolocation of the SPOT5 reference image will propagate in all the steps of the DEM generation and can lead to a shifted SPOT5-DEM. 

Q7. What is the effect of the roll anomalies on the SPOT5-DEM?

Note that the anomalies of the roll of the 13 November 2004 image and of the pitch and yaw (the two other parameters describing the attitude of satellite) for both SPOT5 images are nearly an order of magnitude smaller than the roll anomalies of the 12 November 2004 image and, consequently, have a limited effect on the SPOT5-DEM. 

Q8. What is the sensitivity to gain/loss material in the accumulation zone?

The sensitivity to the density of gain/loss material in the accumulation zone depends (obviously) on the size of the accumulation area relative to the whole glacier area. 

Q9. How do you get the resulting errors in the SPOT5 elevations?

The resulting errors in the SPOT5 elevations are roughly obtained by dividing this horizontal shift by the base-to-height ratio (B/H = 0.61) for this pair of image (Toutin, 2002). 

Q10. Why are the elevation changes in the Himalaya less accurate than in the Alps?

their elevation changes are less accurate in Himalaya than in the Alps but, due to the lack of ground truth data, the authors cannot provide here an uncertainty.