Hindu Kush, Karakorum, Himalaya and Tibetan Plateau Glaciers: Tipping Point - Impact of Global Changes on Mountains: Responses and Adaptation - page 316

refl ect monsoon dynamics and are down wasting (i.e., stationary decaying)
instead of just retreating in response to atmospheric warming (Hasnain
2010). There has been shrinkage of 5.5% in the volume of glaciers in China
and similar rates are found in Nepal, India and Bhutan (Edwards et al. 2010).
Glaciers in the eastern and central part of Himalaya are expected
to be especially sensitive to present atmospheric warming, due to their
summer-accumulation type nature (Ageta and Higuchi 1984). An increase
in summer air temperature not only enhances ice melt but also signifi cantly
reduces the accumulation by altering snowfall to rain. In contrast, winter-
accumulation type glaciers receive their main accumulation at lower
temperatures and are thus less sensitive to an increase in air temperatures.
Rapid retreat in plateau glaciers is presumably driven by warming due to
increasing greenhouse gases and by black carbon or soot (Baiqing et al. 2009).
Quantitative modeling of the effect of black soot on glacier dynamics is a
current challenge, but some indication in studies by (Yasunari et al. 2010)
suggest that black soot is responsible for a secondary factor that drives
substantial melting in glaciers.
Given the size and remoteness of glaciers in the Himalaya, satellite
imagery is widely used to obtain a comprehensive regional estimate of
glacier mass balance. Recently, in Bhutan, glacier retreat shows a north-
south gradient with larger retreat rates in the south as the infl uence of the
monsoon decreases towards the north, according to the studies conducted
by Kaab (2005). He combined ASTER and SRTM (Shuttle Radar Topographic
Mission) data to produce synthetic digital elevation model and then map
the contrasted dynamical behavior of north and south facing glaciers in the
northernmost section Bhutan Himalaya ridge (called 'Lunana'; 28ºN, 90-91º
E) separating the Tibetan plateau to the north from the central Himalaya
to the south. The northbound glacier tongues show speeds of several tens
to over 200 m year -1 . They are almost debris free as the ice fl ux drains the
large accumulation areas through the northbound valleys, in order to keep
the glacier in geometric equilibrium. In contrast the southern glaciers have
high debris cover and velocity around 40 m y -1 near the tongues, which
appear to be nearly stagnant. The response to atmospheric warming for
these glacier tongues is down wasting—essentially decoupled from the
dynamics of upper glacier parts. Most of the Himalaya glaciers south of
ridge lie in a warm and humid climate system are down wasting, blocks
dead ice having no or loose contact with the active part of glacier. As a
consequence moraine dammed glacier lakes are commonly formed at
the glacier tongues. Studies by (SAC 2011) on three basins from Ganga,
Brahmaputra and Indus show upward movement of snowline and negative
mass balance for large number of glaciers. The Kolahoi, Indian Kashmir the
biggest glacier and principal source of water to Jhelum River has shrunk
over 3 km 2 during the past three decades (Hasnain 2010). Similarly, the