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
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
CC compared to 1980 1999 IPCC 2007 (A1B scenario) 2020-2029 2090-2099 T [ C] Winter (2090-2099) Summer (2090-2099) Precip [%]
All-Nepal Temperature Trends Regional Mean Temperature Trends for the period 1977-2000 ( C per year) Seasonal Annual Regions Winter Pre-monsoon Monsoon Post-monsoon Jan-Dec Dec-Feb Mar-May Jun-Sep Oct-Nov Trans-Himalaya 0.12 0.01 0.11 0.10 0.09 Himalaya 0.09 0.05 0.06 0.08 0.06 Middle Mountains 0.06 0.05 0.06 0.09 0.08 Siwalik 0.02 0.01 0.02 0.08 0.04 Terai 0.01 0.00 0.01 0.07 0.04 All-Nepal 0.06 0.03 0.051 0.08 0.06 Update after Shrestha et al. 1999
Elevation-Temperature Trend Relationship (Tibetan Plateau) Liu and Chen, 2000
Regional Trends- HKH Temperature Anomaly ( o C) 3 2 1 0-1 -2-3 a. b. y = -184.44 + 0.093 x R= 0.65632 µ=-3.09 σ=0.39 y = -161.57 + 0.081443x R= 0.59188 µ=8.09 σ=0.33 3 2 1 0-1 -2 Temperature Anomaly ( o C) Temperature Anomaly ( o C) 3 2 1 0-1 -2-3 c. y = -134.43 + 0.068 x R= 0.49862 µ=20.22 σ=0.31 d. 1960 1970 1980 1990 2000-3 Shrestha 2009
Precipitation Change - India Goswami and Ramanathan, 2007
Extreme rainfall events Nepal Number of rainy days y = -0.0576x + 103.76 120 R 2 = 0.0072 115 110 105 100 Less rainy days Days 95 90 85 80 75 70 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 Year Number of days with rain >= 100 mm y = 0.5997x + 61.417 R 2 = 0.0984 Days 120 100 80 60 40 1975 1977 1982 1987, 106 1998 1992, 35 More intense rainfall events 20 0 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 Year (Adopted from Baidya and Regmi, 2007)
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
Zone of ablation
Types of glaciers http://nsidc.colorado.edu/glaciers Piedemont Icefields Hanging glacier Ice Cap Outlet Mountain Valley
River valley/glacial valley http://library.thinkquest.org
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
Are HKH glacier retreating?
Rika Samba Glacier 1974 1994 200 m SOURCE: GEN/DHM RESEARCH
Glacier AX010, Nepal SOURCE: GEN/DHM RESEARCH
Fluctuation of EB050 glacier 1997 2004
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% 1950-1970 1970-1980 1980-1990 1990-Present Tandong et al., 2004
Scherler et al., 2011; Nature Geoscience
Scherler et al., 2011; Nature Geoscience
Bajracharya (In prep) Number of Glacier 4000 3500 3000 2500 2000 1500 1000 500 0 +9% 2001 2009 Series1 Series2
Bajracharya (In prep) Area of Glaciers 6000 5000 4000 3000 2000-20% 2001 2009 Series1 Series2 1000 0
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.
Miller et al., DFID System. Rev. What is the evidence about glacier melt across the Himalaya (in Prep.) http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo1068.html. 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
Are HKH glaciers going to vanish? When?
Climate change debate
How does a glacier operate? Melting
Kaser, 2008
Kaser, 2008
Kaser, 2008
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
Himalayan Glaciers are Melting Faster than Anywhere else!
Lemke et al. (2007) - IPCC 2007 AR4 WG I, Ch. 4
Consequences
Changes in Runoff over Time: Seasonal and long term (redrawn from Kaser, unpublished)
Scientific uncertainties? How? How much? Where? When? Challenging environment Limited baseline information Low capacity Low awareness
Langtang, Nepal Q (m 3 /s) 14 12 10 8 6 rain baseflow snow glacier (mm) 1200 900 600 300 0 Glacial runoff Snow runoff Rain runoff Baseflow 4 2005 2025 2050 2075 2 0 2001 2011 2021 2031 2041 2051 2061 2071 2081 2091 Immerzeel et al., Climatic Change (Accepted)
Rees et al. (2004) T=0.06oC/yr P=15%/yr
UNEP, 2007
Thank you Thanks to global warming