Ash and its effect on Snowpack

Winter Ecology: Spring 2014Mountain Research Station,

University of Colorado, BoulderBy: Jessica Walker

Introduction

• Albedo: how much light is reflected from a surface– Pure snow= ~.95– Polluted snow= .45-.19

• Why should we care?– Climate change – Runoff and Spring melt

earlier → greater water stress in late summerImage from Westernviews.org

• Ways that previous research has looked at changing albedo:– Dust Storms (Painter et. al.)– Soot and ash (Conway et.al.)

• Why does ablation occur? Positive Feedback!

Image from TheCelestialConvergence.blogspot.com

My Research

Question: How will the addition of ash affect the snow pack structure and

depth of sites via change in albedo?

Hypothesis: The addition of ash will cause increased grain size and increased

temperatures. Melting more likely in the treatment sites, so may see lower snow depth compared to control.

Null Hypothesis:Ash will have no effect on the snowpack and snowpack structure will

be uniform throughout the three conditions.

Methods• 3 conditions: Control, light ash and heavy ash• Open field off of Niwot Rd. All plots had same aspect, elevation and

depth (1.05m)• Snow pits!

– Dug one when establishing sites and 3 (one through each site) one week later• Analysis

– Snow Pilot to map layers and temperature

ResultsD

epth

(cm

)

• New snow layer not consistent

• Ash conditions softer, no ash layer

• Very little temperature variation in heavy ash condition

• Ash layer placement

• Ash moved down in pack

Discussion

• Ash migrated down within the snowpack • Larger grain size and more rounding• Seemingly large difference in depth– Unable to determine whether significant

• Implications– Subnivean temperature– Summer water stress

• Future replication– More pits– Vary them in orientation

Summary

• Ash lowers albedo significantly• My experiment found that more melt

occurred in the heavy ash condition– Also more rounding and sintering– Also less of temperature gradient

• Need more replicates to determine whether depth difference was significant

References• Conway, H., Gades, A., Raymond, C.F. “Albedo of dirty snow during

conditions of melt.” Water Resources Research. Vol. 32, No. 6, pp. 1713-1718, June 1996. http://www.atmos.washington.edu/sootinsnow/PDF_Documents/Albedo%20of%20Dirty%20Snow%20During%20Melt.pdf

• Guido, Zack. “Cinnamon snow: flecks of dust alter Western water supplies.” CLIMAS Southwest Climate Outlook. The University of Arizona. 2013. http://www.southwestclimatechange.org/feature-article/snow-dust

• Hansen, James and Larissa Nazarenko. “Soot Climate Forcing via Snow and Ice Albedos.” PNAS. January 2004. Vol. 101, no. 2, pp. 423-428.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC327163/pdf/1010423.pdf • Painter, T., Skiles, S., Deems, J., Bryant, C., Landry, C. “Dust radiative forcing

in snow of upper Colorado River basin: 1. A 6 year record of energy balance, radiation, and dust concentrations.” Water Resources Research. Vol. 48, W07521, 2012. https://jifresse.ucla.edu/press/Painteretal_DustRadiative.pdf

Acknowledgments

Thanks Derek Sweeney for your help with equipment and Tim Kittel for your help in making sense of everything. Also Amanda

Tynan for hiking to my site with me.