Rapid downwasting of lower portion of Ponkar Glacier and its impacts in Manang, Nepal
Abstract
Quantifying and understanding the dynamics of melting of the underlying ice has always been a challenge especially in the rough terrains of the Himalayas. This study incorporates the use of Unmanned Aerial Vehicle (UAV) to analyze the downwasting of Ponkar Glacier, Manang, Nepal Himalayas. Four repeat aerial surveys have been conducted using a Quad Copter and a fixed wing UAVs on the lower part of the glacier. The surveys have been conducted in March and July 2016 (quad copter) and in November 2016 and May 2017 (fixed wing). Three ablation stakes are also installed on the survey region of the glacier so as to compare the ice melt. Comparing the high resolution DEMs (2 and 10 cm) generated from those aerial surveys, downwasting of the glacier is found to be ranging from 0.68 m to 0.94 m under the debris thickness of 11 and 20 cm, respectively from 20 March to 5 July 2016. Similarly, average downwasting of the lower part of the glacier is found to be 0.47 m since 14 November 2016 to 5 May 2017. The downwasting follows a heterogeneous pattern across the glacier. The net ablation of 2.04 and 2.21 m are found at debris thickness of 11 and 20 cm from March 2016 to May 2017, respectively. Alongside that, a 16 MHZ Multi Low frequency Ground Penetrating Radar (GPR) has also been used to estimate the underlying ice thickness. The result indicates thickness of 80 m near the terminus of the glacier. To address the change in the glacier to the changing climate, the meteorological conditions prevailing in the valley also needs to be properly understood. Hence, six precipitation gauges and temperature sensors have been installed along the downstream valley of the glacier at different elevations ranging from 1926 to 3780 m asl. Based on the observed data, average vertical and longitudinal precipitation gradients of the valley have been found to be 2.9 % m-1 and -0.45 % m-1, respectively. Likewise, the temperature lapse rate has been found to be -0.0088 °C m-1. These preliminary results of the ongoing study on Ponkar Glacier and future similar repeat surveys of the glacier would provide a much larger temporal scale and a far better understanding of the glacier melt variations and its impact on water availability in the downstream.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.C33A1167K
- Keywords:
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- 0720 Glaciers;
- CRYOSPHERE;
- 0762 Mass balance 0764 Energy balance;
- CRYOSPHERE;
- 1621 Cryospheric change;
- GLOBAL CHANGE;
- 1827 Glaciology;
- HYDROLOGY