Satellite observations of desert dust‐induced Himalayan snow darkening

Gautam, Ritesh; Hsu, N. Christina; Lau, William K. M.; Yasunari, Teppei J.

doi:10.1002/grl.50226

Cited by 152 publications

(110 citation statements)

References 37 publications

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“…Neglecting additional RFS from LAISI other than BC is likely to result in an underestimation of the overall effect of LAISI on snowmelt and discharge generation. Especially the contribution from dust is critical since it has been shown that in many regions such as the Rocky Mountains , Utah , the southern edge of the Himalayas (Gautam et al, 2013), and Svalbard , dust can play a significant role in terms of RFS or even is the dominating LAISI. For Norway, however, analysis conducted by Forsström et al (2013) indicates that dust might only play a minor role.…”

Section: Uncertaintiesmentioning

confidence: 99%

Modelling hydrologic impacts of light absorbing aerosol deposition on snow at the catchment scale

Matt

Burkhart

Pietikäinen

2018

Hydrol. Earth Syst. Sci.

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Abstract. Light absorbing impurities in snow and ice (LAISI) originating from atmospheric deposition enhance snowmelt by increasing the absorption of shortwave radiation. The consequences are a shortening of the snow duration due to increased snowmelt and, at the catchment scale, a temporal shift in the discharge generation during the spring melt season.In this study, we present a newly developed snow algorithm for application in hydrological models that allows for an additional class of input variable: the deposition mass flux of various species of light absorbing aerosols. To show the sensitivity of different model parameters, we first use the model as a 1-D point model forced with representative synthetic data and investigate the impact of parameters and variables specific to the algorithm determining the effect of LAISI. We then demonstrate the significance of the radiative forcing by simulating the effect of black carbon (BC) deposited on snow of a remote southern Norwegian catchment over a 6-year period, from September 2006 to August 2012. Our simulations suggest a significant impact of BC in snow on the hydrological cycle. Results show an average increase in discharge of 2.5, 9.9, and 21.4 %, depending on the applied model scenario, over a 2-month period during the spring melt season compared to simulations where radiative forcing from LAISI is not considered. The increase in discharge is followed by a decrease in discharge due to a faster decrease in the catchment's snow-covered fraction and a trend towards earlier melt in the scenarios where radiative forcing from LAISI is applied. Using a reasonable estimate of critical model parameters, the model simulates realistic BC mixing ratios in surface snow with a strong annual cycle, showing increasing surface BC mixing ratios during spring melt as a consequence of melt amplification. However, we further identify large uncertainties in the representation of the surface BC mixing ratio during snowmelt and the subsequent consequences for the snowpack evolution.

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Section: Uncertaintiesmentioning

confidence: 99%

Modelling hydrologic impacts of light absorbing aerosol deposition on snow at the catchment scale

Matt

Burkhart

Pietikäinen

2018

Hydrol. Earth Syst. Sci.

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“…Both radiative transfer models (Aoki et al, 2011;Hadley and Kirchstetter, 2012;Warren and Wiscombe, 1980) and direct measurements (Bryant et al, 2013;Doherty et al, 2013;Gautam et al, 2013;Painter et al, 2010Painter et al, , 2012Skiles and Painter, 2017) demonstrate that even small amounts of light absorbing impurities (LAIs) affect the surface albedo of snow significantly. Black carbon and desert dust are the main sources of LAI in snow, but algal blooms and organic carbon could also play a role.…”

Section: Introductionmentioning

confidence: 99%

The importance of snow albedo for ice sheet evolution over the last glacial cycle

Willeit

Ganopolski

2018

Clim. Past

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Abstract. The surface energy and mass balance of ice sheets strongly depends on the amount of solar radiation absorbed at the surface, which is mainly controlled by the albedo of snow and ice. Here, using an Earth system model of intermediate complexity, we explore the role played by surface albedo for the simulation of glacial cycles. We show that the evolution of the Northern Hemisphere ice sheets over the last glacial cycle is very sensitive to the representation of snow albedo in the model. It is well known that the albedo of snow depends strongly on snow grain size and the content of lightabsorbing impurities. Excluding either the snow aging effect or the dust darkening effect on snow albedo leads to an excessive ice build-up during glacial times and consequently to a failure in simulating deglaciation. While the effect of snow grain growth on snow albedo is well constrained, the albedo reduction due to the presence of dust in snow is much more uncertain because the light-absorbing properties of dust vary widely as a function of dust mineral composition. We also show that assuming slightly different optical properties of dust leads to very different ice sheet and climate evolutions in the model. Conversely, ice sheet evolution is less sensitive to the choice of ice albedo in the model. We conclude that a proper representation of snow albedo is a fundamental prerequisite for a successful simulation of glacial cycles.

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“…Furthermore, there is evidence that dust deposition in the Himalaya may be increasing due to anthropogenic activities and increased aridity (e.g., Thompson et al, 2000;Kaspari et al, 2009), and recent remote sensing studies suggest that dust may dominate solar absorption (Gautam et al, 2013;Ming et al, 2012). However, the lack of in situ data from this region prevents evaluating the effect of BC and dust deposition on snow and ice albedo and melt.…”

Section: Introductionmentioning

confidence: 99%

Seasonal and elevational variations of black carbon and dust in snow and ice in the Solu-Khumbu, Nepal and estimated radiative forcings

et al. 2014

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Abstract. Black carbon (BC) and dust deposited on snow and glacier surfaces can reduce the surface albedo, accelerate snow and ice melt, and trigger albedo feedback. Assessing BC and dust concentrations in snow and ice in the Himalaya is of interest because this region borders large BC and dust sources, and seasonal snow and glacier ice in this region are an important source of water resources. Snow and ice samples were collected from crevasse profiles and snow pits at elevations between 5400 and 6400 m a.s.l. from Mera glacier located in the Solu-Khumbu region of Nepal during spring and fall 2009, providing the first observational data of BC concentrations in snow and ice from the southern slope of the Himalaya. The samples were measured for Fe concentrations (used as a dust proxy) via ICP-MS, total impurity content gravimetrically, and BC concentrations using a Single Particle Soot Photometer (SP2). Measured BC concentrations underestimate actual BC concentrations due to changes to the sample during storage and loss of BC particles in the ultrasonic nebulizer; thus, we correct for the underestimated BC mass. BC and Fe concentrations are substantially higher at elevations < 6000 m due to post-depositional processes including melt and sublimation and greater loading in the lower troposphere. Because the largest areal extent of snow and ice resides at elevations < 6000 m, the higher BC and dust concentrations at these elevations can reduce the snow and glacier albedo over large areas, accelerating melt, affecting glacier mass balance and water resources, and contributing to a positive climate forcing. Radiative transfer modeling constrained by measurements at 5400 m at Mera La indicates that BC concentrations in the winter-spring snow/ice horizons are sufficient to reduce albedo by 6-10 % relative to clean snow, corresponding to localized instantaneous radiative forcings of 75-120 W m −2 . The other bulk impurity concentrations, when treated separately as dust, reduce albedo by 40-42 % relative to clean snow and give localized instantaneous radiative forcings of 488 to 525 W m −2 . Adding the BC absorption to the other impurities results in additional radiative forcings of 3 W m −2 . The BC and Fe concentrations were used to further examine relative absorption of BC and dust. When dust concentrations are high, dust dominates absorption, snow albedo reduction, and radiative forcing, and the impact of BC may be negligible, confirming the radiative transfer modeling. When impurity concentrations are low, the absorption by BC and dust may be comparable; however, due to the low impurity concentrations, albedo reductions are small. While these results suggest that the snow albedo and radiative forcing effect of dust is considerably greater than BC, there are several sources of uncertainty. Further observational studies are needed to address the contribution of BC, dust, and colored organics to albedo reductions and snow and ice melt, and to characterize the time variation of radiative forcing.

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Satellite observations of desert dust‐induced Himalayan snow darkening

Cited by 152 publications

References 37 publications

Modelling hydrologic impacts of light absorbing aerosol deposition on snow at the catchment scale

Modelling hydrologic impacts of light absorbing aerosol deposition on snow at the catchment scale

The importance of snow albedo for ice sheet evolution over the last glacial cycle

Seasonal and elevational variations of black carbon and dust in snow and ice in the Solu-Khumbu, Nepal and estimated radiative forcings

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