名古屋大学グローバルCOEプログラム 地球学から基礎・臨床環境学への展開

BCES

セミナー

Climate change and adaptation research in the Himalayan region - Challenges and need for collaboration

スケジュール

2013年8月7日(金)13:30~15:30
環境共用館3階 大講義室

講演者

Shreedhar Maseky (UNESCO-IHE, Netherlands)
Koji Fujita (GSES, Nagoya Univ.)
Akiko Sakai (GSES, Nagoya Univ.)

問い合わせ

藤田耕史(環境学研究科地球環境科学専攻・准教授)

詳細

Talk 1
Climate change and adaptation research in the Himalayan region - Challenges and need for collaboration

Speaker: Shreedhar Maseky (UNESCO-IHE, Netherlands)

Abstract: Amidst growing concerns over the melting of the Himalayas' snow and glaciers under climate change, in this seminar Dr. Maskey will present some of the research results on climate change, hydrological modelling and climate-crop yield-adaptation in Himalayan river basins. He will also present some of the key challenges of modelling climate change impacts in the region.


Talk 2
Potential flood volume of Himalayan glacial lakes
http://www.nat-hazards-earth-syst-sci.net/13/1827/2013/nhess-13-1827-2013.html
http://news.sciencemag.org/sciencenow/2013/07/satellites-could-predict-hazards.html

Speaker: Koji Fujita (GSES, Nagoya Univ.)

Abstract: Glacial lakes are potentially dangerous sources of glacial lake outburst floods (GLOFs), and represent a serious natural hazard in Himalayan countries. Despite the development of various indices aimed at determining the outburst probability, an objective evaluation of the thousands of Himalayan glacial lakes has yet to be completed. In this study we propose a single index, based on the depression angle from the lakeshore, which allows the lakes to be assessed using remotely sensed digital elevation models (DEMs). We test our approach on five lakes in Nepal, Bhutan, and Tibet using images taken by the declassified Hexagon KH-9 satellite before these lakes experienced an outburst flood. All five lakes had a steep lakefront area (SLA), on which a depression angle was steeper than our proposed threshold of 10° before the GLOF event, but the SLA was no longer evident after the events. We further calculated the potential flood volume (PFV); i.e., the maximum volume of floodwater that could be released if the lake surface was lowered sufficiently to eradicate the SLA. This approach guarantees repeatability to assess the possibility of GLOF hazards because it requires no particular expertise to carry out, though the PFV does not quantify the GLOF risk. We calculated PFVs for more than 2000 Himalayan glacial lakes using visible band images and DEMs of ASTER data. The PFV distribution follows a power-law function. We found that 794 lakes did not have an SLA, and consequently had a PFV of zero, while we also identified 49 lakes with PFVs of over 10 million m3, which is a comparable volume to that of recorded major GLOFs. This PFV approach allows us to preliminarily identify and prioritize those Himalayan glacial lakes that require further detailed investigation on GLOF hazards and risk.


Talk 3
Climate regime of Asian glaciers revealed with the GAMDAM glacier inventory

Speaker: Akiko Sakai (GSES, Nagoya Univ.)

Abstract: Glacier inventories provide a basic information for the water resources, glacier mass balance and ice volume at continental areas. Although glaciers in the Asian mountain are thought to play an important role for the regional water resources (Immerzeel et al., 2010), glacier distribution in the Asia have been poorly understood.
Our GAMDAM (Glacier Area Mapping for Discharge in Asian Mountains) project have conducted to establish a glacier inventory with the aim of estimating glacier runoff contribution to river runoff. Our target region covers the High Mountain Asia, extending from 27 to 52 degrees N and from 68 to 104 degrees E.
Glacier outlines were manually delineated using more than 260 of LANDSAT images taken from 1999 to 2003. Thermal infrared band was also used to delineate termini of debris-covered glaciers with help of high resolution images on Google Earth. The manual delineation has been conducted for more than two years by 5-7 operators. We conducted several tests, along which the operators delineated the same regions, and assessed the quality and criteria, and fed them back to the operators. At the end of June 2013, the inventory was completed 80% with about 63000 glaciers covering 7.8 × 10^4 km^2.
Median elevation of glaciers has been interpreted as a proxy for the equilibrium line altitude (ELA), at which the accumulation and ablation were equal and thus the mass balance was zero (Braithwaite and Raper, 2009). Distribution of the median altitude derived from the GAMDAM glacier inventory was well consistent with that previously reported (Shi et al., 1980). We calculated glacier mass balance over the median altitude using the NCEP/NCAR reanalysis dataset (Kalnay et al., 1996) and the Aphrodite precipitation dataset (Yatagai et al, 2009), through which the precipitation was optimized to result in the zero mass balance for decadal scale. The calculated precipitation shows highly contrasted distribution compared to the original one, and exhibited a reasonable relationship among precipitation and summer mean temperature at the ELA, which has been previously studied with observational data worldwide. We also conducted a sensitivity analysis, and revealed large spatial variability of response of glacier over the High Mountain Asia, supporting recent remote sensing analyses.

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