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All Posts By Alia Khan

Black Carbon in the Cryosphere

I’m very excited to join the field team this summer! My contribution to Dark Snow’s Greenland ice sheet field campaign this summer is to quantify changes in spectral albedo over the melt season using an Analytical Spectral Device (ASD) portable spectrometer. A related objective for my doctoral research on Black Carbon in the Cryosphere is to collect black carbon samples.

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Collecting spectral reflectance measurements of dirty snow in Svalbard

Black Carbon (BC) comes from incomplete combustion of biomass and fossil fuels (Goldberg et al., 1985). On snow and ice, the dark particles absorb sunlight, substantially reducing the surface albedo. The absorption heats the surrounding matter, promoting melt. This feedback is of particular importance in polar and alpine regions dominated by snow and ice. In this sense, Greenland and the Himalayas share this enhanced climate sensitivity. Black carbon deposition on the Greenland ice sheet enhances generation of melt-water, which contributes to further melting of the ice sheet, as well global sea level rise.

Researchers have been studying the effect black carbon has on the cryosphere and black carbon’s linkage with global climate for decades (Wiscombe and Warren, 1980; Grenfell et al., 1981, Chylek et al., 1983; Clarke and Noone 1985; Hadley et al., 2010). Although advancements in remote sensing enable quantitative measurements of aerosol black carbon in the atmosphere, remote sensing of black carbon in snow is not currently possible (Warren, 2013). Ground measurements of the cryosphere, such as with a portable spectrometer, therefore remain one of the only ways to monitor and quantify surface albedo reductions due to black carbon.

Recent developments in chemical and optical analytical techniques are enabling more descriptive studies of black carbon within snow and ice (Hegg et al. 2009, Kaspari et al. 2011, Schwarz et al. 2012). Black carbon aerosols from both biomass burning and fossil fuel combustion may travel across the globe in the atmosphere, and are then ‘scavenged’ by rain or snow precipitation (Doherty et al., 2010). Furthermore, after deposition they become retained in the snowpack or ice surface where they may degrade over time.

The aim of our work this summer is to measure spectral albedo change through the microbial ‘growing season’, as well as to discern how black carbon concentrations may relate to growth of microbes. The data I collect will contribute to my dissertation research that so far has focused on the Dry Valleys of Antarctica, Nepalese Himalayas, and the Norwegian Arctic. Like snowflakes, each system is unique; with different sources of black carbon, as well as varying impacts. In the Himalayas there are both local and long-range transport sources of black carbon, and increased melting can have an impact on water resources for downstream communities. In Greenland, most black carbon comes from long-range transport and has major implications on increasing melt-water generation, which leads to further and more rapid loss of ice, as well as sea level rise. Due to rapid surface melting, the Greenland ice sheet is a highly dynamic system to study impurities on the ice surface, as well as to understand their impacts on ice melt. Thus, I’m really excited to forage in another different system.

Gearing up for the upcoming field season, I am filled with a variety of feelings. Life as a grad student is often very busy, with a variety of projects and commitments, but field experiences like this where you have the opportunity to be on the ground collecting data, seeing and experiencing changes in the cryosphere first hand, is what it’s all about for me. I’m really looking forward to being a part of the Dark Snow team!

Alia Khan – PhD student at the University of Colorado, Boulder / Institute of Arctic and Alpine Research (INSTAAR).

References:

Chýlek, P. (1983). Albedo of soot?contaminated snow. Journal of Geophysical Research, 88(3), 837–843. doi/10.1029/JC088iC15p10837/full

Clarke, A., and Noone, J. (1985). SOOT IN THE ARCTIC SNOWPACK: A CAUSE FOR PERTURBATIONS IN RADIATIVE TRANSFER, 19(12), 2045–2053.

Grenfell, T. C., Perovich, D. K., & Ogren, J. A. (1981). SPECTRAL ALBEDOS OF AN ALPINE SNOWPACK Thomas C. Grenfell and Donald K. Perovich, 4, 121–127.

Hadley, O. L., Corrigan, C. E., Kirchstetter, T. W., Cliff, S. S., & Ramanathan, V. (2010). Measured black carbon deposition on the Sierra Nevada snow pack and implication for snow pack retreat. Atmospheric Chemistry and Physics, 10(15), 7505–7513. doi:10.5194/acp-10-7505-2010

Hegg, D. a, Warren, S. G., Grenfell, T. C., Doherty, S. J., Larson, T. V, & Clarke, A. D. (2009). Source attribution of black carbon in Arctic snow. Environmental Science & Technology, 43(11), 4016–21. http://www.ncbi.nlm.nih.gov/pubmed/19569324

Kaspari, S. D., Schwikowski, M., Gysel, M., Flanner, M. G., Kang, S., Hou, S., & Mayewski, P. a. (2011). Recent increase in black carbon concentrations from a Mt. Everest ice core spanning 1860-2000 AD. Geophysical Research Letters, 38(4), doi:10.1029/2010GL046096

Schwarz, J. P., Doherty, S. J., Li, F., Ruggiero, S. T., Tanner, C. E., Perring, a. E., … Fahey, D. W. (2012). Assessing recent measurement techniques for quantifying black carbon concentration in snow. Atmospheric Measurement Techniques Discussions, 5(3), 3771–3795. doi:10.5194/amtd-5-3771-2012

Warren, S. G. (2013). Can black carbon in snow be detected by remote sensing? Journal of Geophysical Research: Atmospheres, 118(2), 779–786. doi:10.1029/2012JD018476

Warren, S. G., & Clarke, A. D. (1990). Soot in the atmosphere and snow surface of Antarctica. Journal of Geophysical Research, 95(D2), 1811. doi:10.1029/JD095iD02p01811