Warming planet, melting glaciers

Transcription

1 Warming planet, melting glaciers Arun B Shrestha abshrestha@icimod.org International Centre for Integrated Mountain Development Kathmandu, Nepal Asia-Pacific Youth forum on Climate Actions and Mountain Issues, 8-12, August 2011

2 Content Projected Climate Change Observed Climate Change What is a glacier? What is glacier retreat or advance? Are HKH glacier retreating? Does retreat or advance tells the complete Story? What are the methods to assess glacial dynamics? Are HKH glaciers going to vanish? When? Himalayan Glaciers are Melting Faster than Anywhere else! Consequences

3 CC compared to IPCC 2007 (A1B scenario) T [ C] Winter ( ) Summer ( ) Precip [%]

4 All-Nepal Temperature Trends Regional Mean Temperature Trends for the period ( C per year) Seasonal Annual Regions Winter Pre-monsoon Monsoon Post-monsoon Jan-Dec Dec-Feb Mar-May Jun-Sep Oct-Nov Trans-Himalaya Himalaya Middle Mountains Siwalik Terai All-Nepal Update after Shrestha et al. 1999

5 Elevation-Temperature Trend Relationship (Tibetan Plateau) Liu and Chen, 2000

6 Regional Trends- HKH Temperature Anomaly ( o C) a. b. y = x R= µ=-3.09 σ=0.39 y = x R= µ=8.09 σ= Temperature Anomaly ( o C) Temperature Anomaly ( o C) c. y = x R= µ=20.22 σ=0.31 d Shrestha 2009

7 Precipitation Change - India Goswami and Ramanathan, 2007

8 Extreme rainfall events Nepal Number of rainy days y = x R 2 = Less rainy days Days Year Number of days with rain >= 100 mm y = x R 2 = Days , , 35 More intense rainfall events Year (Adopted from Baidya and Regmi, 2007)

9 What is a glacier? A glacier is a large body of ice, in which ice from a higher elevation is transported to a lower elevation. The body of ice must be at least 30 metres thick for this to take place. The movement of the ice is always from the upper part of the glacier towards the lower end (the snout), regardless of whether the glacier is advancing or retreating. ICIMOD 2009; HKH glacier FAQ

10 Zone of ablation

11

12 Types of glaciers Piedemont Icefields Hanging glacier Ice Cap Outlet Mountain Valley

13 River valley/glacial valley

14 What is glacier retreat or advance? A glacier is said to retreat or advance when the position of the end (terminus or snout) of the glacier changes, retreating higher up the slope or advancing down the slope. ICIMOD 2009; HKH glacier FAQ

15 Are HKH glacier retreating?

16 Rika Samba Glacier m SOURCE: GEN/DHM RESEARCH

17 Glacier AX010, Nepal SOURCE: GEN/DHM RESEARCH

18 Fluctuation of EB050 glacier

19 Gangotri, India Tibet, China Deglaciation is widespread in HKH Some advances in Hindu Kush and Karakorum Status of Glaciers in Tibetan Plateau J. Kargel, USGS 100% 90% 80% 70% 60% 50% Stationary Advancing Retreating 40% 30% 20% 10% 0% Present Tandong et al., 2004

20 Scherler et al., 2011; Nature Geoscience

21 Scherler et al., 2011; Nature Geoscience

22 Bajracharya (In prep) Number of Glacier % Series1 Series2

23 Bajracharya (In prep) Area of Glaciers % Series1 Series

24 Does retreat or advance tells the complete Story? In general, a change in the position of a glacier snout is a good indication of change taking place in the total amount of ice in the glacier But the relationship is not direct; the position of the snout is only an indicator, it does not give exact information about changes (or otherwise) in the amount of ice in the glacier.

25 Miller et al., DFID System. Rev. What is the evidence about glacier melt across the Himalaya (in Prep.) What are the methods to assess glacial dynamics? Relative confidence rating of method with increasing confidence signalling greater accuracy and scientific rigour Very low Very high Low High Massbalance Volume Change Area change Terminus shift Vertical balance profile / Climate records Thickness profiling & Field Mapping Description Description Flux divergence method Remote sensing with baseline field mapping Terrestrial photography Terrestrial photography Hydrological method Remote sensing and digital elevation model Field mapping / Mapping from aerial photographs Field mapping / Mapping from aerial photographs Geodetic method / Remote sensing Remote sensing with baseline geo-referenced field mapping Remote sensing with baseline geo-referenced field mapping Glaciological method Remote sensing Remote sensing

26 Are HKH glaciers going to vanish? When?

27 Climate change debate

28 How does a glacier operate? Melting

29 Kaser, 2008

30 Kaser, 2008

31 Kaser, 2008

32 An example The average position of the zero degree isotherm (ZDI) in the Himalayan ranges is thought to be around 5400 metres above sea level (masl). Above this altitude, the free air temperature never rises above zero. The ZDI is an approximate indicator of the level above which glaciers accumulate ice. The accumulation zones of most Himalayan glaciers extend much higher than this elevation. As overall temperatures rise, the position of the ZDI will also move to higher altitude. For example, a 4 C rise in temperature would cause the ZDI to rise by about 650m to 6050 masl. Even at this level, many of the Himalayan glaciers will still lie above the ZDI and will continue to exist. Equally, large glaciers

33 Himalayan Glaciers are Melting Faster than Anywhere else!

34 Lemke et al. (2007) - IPCC 2007 AR4 WG I, Ch. 4

35 Consequences

36

37 Changes in Runoff over Time: Seasonal and long term (redrawn from Kaser, unpublished)

38 Scientific uncertainties? How? How much? Where? When? Challenging environment Limited baseline information Low capacity Low awareness

39 Langtang, Nepal Q (m 3 /s) rain baseflow snow glacier (mm) Glacial runoff Snow runoff Rain runoff Baseflow Immerzeel et al., Climatic Change (Accepted)

40 Rees et al. (2004) T=0.06oC/yr P=15%/yr

41 UNEP, 2007

42 Thank you Thanks to global warming