Retention and radiative forcing of black carbon in eastern Sierra Nevada snow
- 1Division of Hydrologic Sciences, Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512, USA
- 2Bren School of Environmental Science & Management, University of California, Santa Barbara, CA 93106, USA
- 3Department of Imaging & Applied Physics, Curtin University of Technology Australia, 78 Murray Street, Perth, WA 6000, Australia
- 4Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109, USA
Abstract. When contaminated by absorbing particles, such as refractory black carbon (rBC) and continental dust, snow's albedo decreases and thus its absorption of solar radiation increases, thereby hastening snowmelt. For this reason, an understanding of rBC's affect on snow albedo, melt processes, and radiation balance is critical for water management, especially in a changing climate. Measurements of rBC in a sequence of snow pits and surface snow samples in the eastern Sierra Nevada of California during the snow accumulation and ablation seasons of 2009 show that concentrations of rBC were enhanced sevenfold in surface snow (~25 ng g–1) compared to bulk values in the snowpack (~3 ng g–1). Unlike major ions, which were preferentially released during the initial melt, rBC and continental dust were retained in the snow, enhancing concentrations well into late spring, until a final flush occurred during the ablation period. We estimate a combined rBC and continental dust surface radiative forcing of 20 to 40 W m−2 during April and May, with dust likely contributing a greater share of the forcing.