Albedo reduction of ice caused by dust and black carbon accumulation: a model applied to the K-transect, West Greenland

Abstract

ABSTRACT. Surface melt in the ablation zone is dominated by atmospheric temperature and surface albedo. We developed a surface mass-balance model with a dynamic component of glacier ice albedo which includes surface properties, clouds and the angle of the sun. The ice albedo reduction is mainly caused by impurity accumulation of non-biological origin such as dust and black carbon (BC), which is currently not included in other surface mass-balance models. Simulations show that dust from meltout is the main source of impurity mass at the melting glacier ice surface, and current rates of atmospheric deposition of dust play only a minor role. However, for BC the atmospheric deposition is the main source where ice melt rates are below 1 m, and atmospheric deposition is most likely from intercontinental transport due to the scarce population and lack of forests in Greenland.

Mapping Ice Algal Blooms in Southwest Greenland From Space

“…Surface darkening in Greenland is tightly coupled to the presence of LAI including mineral dust (Wientjes et al, 2011), black carbon (Goelles & Bøggild, 2017), cryoconite (Chandler et al, 2015), and algal blooms (Stibal et al, 2015Williamson et al, 2018;Yallop et al, 2012). These LAI affect the albedo at ultraviolet and visible wavelengths (Tedesco, Box, et al, 2016;Tedesco, Doherty, et al, 2016;Warren, 1982).…”

Radiative Forcing by Dust and Black Carbon on the Juneau Icefield, Alaska

“…The process of consolidation of LAP on the snow surface enhances melt rates via surface darkening and snow grain coarsening, setting up a positive feedback in which the enhanced melting further amplifies surface concentrations of LAP (Warren & Wiscombe, ). Melt amplification has been shown to be an important factor in ice melt in other regions of the world such as on the Greenland ice sheet (Goelles & Bøggild, ; Tedesco et al, ), glaciers in the Himalayas (Kaspari et al, ; Xu et al, ; Yasunari et al, ), Colorado Rockies (Skiles & Painter, ), Alps (Tuzet et al, ), Japan (Aoki et al, ), and in several Arctic sites (northern Alaska, Greenland, and Norway; Doherty et al, ).…”

Satellite Remote Sensing of the Greenland Ice Sheet Ablation Zone: A Review

“…Where snow is present, snow grain growth is the strongest modifier of surface albedo [252,253]. Bare ice albedo is scale dependent but is principally controlled by air bubble size and shape distribution, shadowing by cracks and crevasses [285,289], and by ice grain metamorphism, surface meltwater presence, and exposure and deposition of mineral and biological light-absorbing impurities (LAI) [51,52,58,253,[290][291][292]. The darkening effect of LAI is particularly apparent in satellite images of the GrIS ablation zone that reveal foliated bands of "dark ice" with anomalously low albedo relative to surrounding ice ( Figure 10) [52,273,293,294].…”

“…Contemporary research on GrIS ablation zone surface reflectance and albedo is focused on understanding and diagnosing agents of albedo change [253]. Important questions remaining unresolved include whether observed reductions in GrIS snow albedo are caused by enhanced snow grain metamorphism due to a warming climate [252], or by deposition of LAI such as dust and black carbon from industrial emissions and/or forest fire [292,303]. These questions cannot currently be answered owing to the spectral and radiometric limitations of existing spaceborne optical sensors and inadequate surface validation measurements [280,304].…”

“…For example, it is unlikely that the albedo-reducing effect of industrial black carbon emissions on relatively clean accumulation zone snow can be detected from space [305,306]. Similarly, it is unknown if bare ice albedo reduction due to deposition or emergence of inorganic mineral LAI can be distinguished using satellite imagery from albedo reduction due to biological LAI [292,301].…”