Baiqing Xu, Tandong Yao, Mo Wang, Ninglian Wang, Junji Cao, James Hansen et al. Baiqing Xu 1, Tandong Yao 1, Mo Wang 1, Ninglian Wang 2, Junji Cao 3, James Hansen 4 et al. 5th Third Pole Environment Workshop and the Sino-German Workshop, Berlin, Germany. December 8-11, 2014 Black carbon in snow over the Third Pole region 1.Institute of Tibetan Plateau Research, CAS, China 2.Cold and Arid Regions Environmental and Engineering Research Institute, CAS, China 3.Institute of Earth Environment, CAS, China 4.NASA Goddard Institute for Space Studies, USA

1. Introduction Temperature is increasing rapidly Temperature is increasing rapidly In Tibetan plateau: Glaciers have been melting at an accelerated rate Glaciers have been melting at an accelerated rate (Xu et al. PNAS, 2009) (Yao et al. NCC, 2012) Glacier retreat in Tibetan Plateau presumably is driven by warming due to increasing greenhouse gases, but the rapidity of glacier retreat and the up-to 0.3 o C warming of per decade during the past 30-year suggest additional mechanisms may be involved.

Incomplete combustion: fossil fuel, biomass, biofuel …… Black carbon under electron microscope  Heats troposphere—Suspended in the atmosphere  Suppress rain--Interacts with the clouds  Reduces snow albedo--Deposited on glacier

Absorption of black soot (Atmospheric Warming) Earth surface reflection Absorption of black carbon in the atmosphere An artist's illustration shows how black soot can serve as the seeds of cloud droplets. Credit: NASA Suppress rainfall: by seeding a larger number of smaller cloud droplets, leading to clouds that are less likely to rain out

Solar radiation Reflectance (Flanner et al., JGR, 2007;2009) Solar radiation Reflectance Black carbon incorporated in snowflakes darkens snow and ice surfaces, increasing surface melt. The added absorption by snow becomes significant when it reaches amounts on the order of 10 ng g -1 or more Sprinkled 1 mg of BC over 1 m 2 of fresh snow 5-day late, -15cm Absorption of black carbon on glaciers

(Yao et al. NCC, 2012) ?

Suresh Babu, et al., GRL, 2011 BC in atmosphere BC in snow

2. Black carbon in Tibetan snow and ice

Unit ： mg m -2 a -1 Westerly Monsoon Himalayas Spatial pattern of annual deposition flux of BC over Tibetan plateau (20 glaciers)

Collapse of the Soviet Union (1991) SP2 method TOR method

BC

Seasonal clusters of air mass trajectories over Muztagh Ata region for the period (Jan Dec 2007)

Community Atmosphere Model (CAM5) was used to simulated the contribution of black carbon emission to the deposition flux on Southeastern Tibetan Plateau : South Asia is a commanding contributor during non-monsoon seasons (October to May) (81%) and on an annual basis (74%), followed by East Asia (14% and 21% correspondingly).

， BC+OC ： 12 W/m ， BC+OC ： 17.5 W/m ， BC+OC ： 27 W/m ， BC+OC ： 2.4% ， BC+OC ： 4.0% 2006 ， BC+OC ： 5.7%

3. Enrichment of black soot in snow

ultrasonic Spectral measurement

Evolution of BC concentration on a glacier in Southeast TP Evolution of the glacier surface albedo

Albedo was reduced ~ 10% due to the enrichment of BC in surface snow, and the RF is about 30 W/m 2 Evolution of BC concentration on a glacier in Muztagh Ata

4. Conclusion We find evidence that black carbon aerosols deposited and enriched with surface melt on Tibetan glaciers have been a significant contributing factor to observed rapid glacier retreat

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