ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-9-26593-2009 Black carbon aerosols and the third polar ice cap Menon S. 1 Koch D. 2 Beig G. 3 Sahu S. 3 Fasullo J. 4 Orlikowski D. 5 Lawrence Berkeley National Laboratory, Berkeley, CA, USA Columbia University/NASA GISS, New York, NY, USA Indian Institute for Tropical Meteorology, Pune, India Climate Analysis Section, CGD/NCAR, Boulder, CO, USA Lawrence Livermore National Laboratory, Livermore, CA, USA 11 12 2009 9 6 26593 26625 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/9/26593/2009/acpd-9-26593-2009.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/9/26593/2009/acpd-9-26593-2009.pdf

Recent thinning of glaciers over the Himalayas (sometimes referred to as the third polar region) have raised concern on future water supplies since these glaciers supply water to large river systems that support millions of people inhabiting the surrounding areas. Black carbon (BC) aerosols, released from incomplete combustion, have been increasingly implicated as causing large changes in the hydrology and radiative forcing over Asia and its deposition on snow is thought to increase snow melt. In India BC from biofuel combustion is highly prevalent and compared to other regions, BC aerosol amounts are high. Here, we quantify the impact of BC aerosols on snow cover and precipitation from 1990 to 2010 over the Indian subcontinental region using two different BC emission inventories. New estimates indicate that Indian BC from coal and biofuel are large and transport is expected to expand rapidly in coming years. We show that over the Himalayas, from 1990 to 2000, simulated snow/ice cover decreases by ~0.9% due to aerosols. The contribution of the enhanced Indian BC to this decline is ~30%, similar to that simulated for 2000 to 2010. Spatial patterns of modeled changes in snow cover and precipitation are similar to observations (from 1990 to 2000), and are mainly obtained with the newer BC estimates.

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