Post-depositional enrichment of black soot in snow-pack and accelerated melting of Tibetan glaciers

Xu, Bin; Cao, Junji; Joswiak, Daniel R.; Liu, Xianqin; Zhao, Huabiao; He, Jiasong

doi:10.1088/1748-9326/7/1/014022

Cited by 124 publications

(126 citation statements)

References 26 publications

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“…The IS parameters are derived from a very limited set of observations, while the ES studies are idealized and designed to test the sensitivity of results to this parameter. Although there is large uncertainty in melt scavenging efficiency, a growing number of observational studies indicate that BC is scavenged inefficiently with melt water (Xu et al, 2012;Doherty et al, 2013;Sterle et al, 2013). From field measurements, Doherty et al (2013) derived BC meltwater scavenging efficiencies ranging from 10 % to 30 %, broadly consistent with the parameters used by Flanner et al (2007).…”

Section: Comparison Of Models and Observationsmentioning

confidence: 53%

An AeroCom assessment of black carbon in Arctic snow and sea ice

et al. 2014

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Abstract. Though many global aerosols models prognose surface deposition, only a few models have been used to directly simulate the radiative effect from black carbon (BC) deposition to snow and sea ice. Here, we apply aerosol deposition fields from 25 models contributing to two phases of the Aerosol Comparisons between Observations and Models (AeroCom) project to simulate and evaluate within-snow BC concentrations and radiative effect in the Arctic. We accomplish this by driving the offline land and sea ice components of the Community Earth System Model with different deposition fields and meteorological conditions from 2004 to 2009, during which an extensive field campaign of BC measurements in Arctic snow occurred. We find that models generally underestimate BC concentrations in snow in northern Russia and Norway, while overestimating BC amounts elsewhere in the Arctic. Although simulated BC distributions in snow are poorly correlated with measurements, mean values are reasonable. The multi-model mean (range) bias in BC concentrations, sampled over the same grid cells, snow depths, and months of measurements, are for a more recent phase of AeroCom models (phase II), compared to the observational mean of 19.2 ng g −1 . Factors determining model BC concentrations in Arctic snow include Arctic BC emissions, transport of extra-Arctic aerosols, precipitation, deposition efficiency of aerosols within the Arctic, and meltwater removal of particles in snow. Sensitivity studies show that the model-measurement evaluation is only weakly affected by meltwater scavenging efficiency because most measurements were conducted in non-melting snow. The Arctic (60-90 • N) atmospheric residence time for BC in phase II models ranges from 3.7 to 23.2 days, implying large inter-model variation in local BC deposition efficiency. Combined with the fact that most Arctic BC deposition originates from extra-Arctic emissions, these results suggest that aerosol removal processes are a leading source of variation in model performance. The multi-model mean (full range) of Arctic radiative effect from BC in snow is 0.15 (0.07-0.25) W m −2 and 0.18 (0.06-0.28) W m −2 in phase I and phase II models, respectively. After correcting for model biases relative to observed BC concentrations in different regions of the Arctic, we obtain a multi-model mean Arctic radiative effect of 0.17 W m −2 for the combined AeroCom ensembles. Finally, there is a high correlation between modeled BC concentrations sampled over the observational sites and the Arctic as a whole, indicating that the field campaign provided a reasonable sample of the Arctic.

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Section: Comparison Of Models and Observationsmentioning

confidence: 53%

An AeroCom assessment of black carbon in Arctic snow and sea ice

et al. 2014

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“…The maximum reported BC in surface snow was at the Meikuang glacier (446 ng g À1 ) in the northeastern TP, at Urumqi glacier No. 1 (Urmq1) (~500 ng g À1 ) in the Tianshan and at Mera La (1290 ng g À1 ) (Kaspari et al, 2014;Xu et al, 2012Xu et al, , 2006. In addition, the maximum reported OC and BC in snow pits at the Zhadang glacier in the central TP was~600 ng g À1 BC, and at Urmq1 was~8000, 3000 ng g À1 .…”

Section: Comparison Of the Results To Other Studiesmentioning

confidence: 97%

“…This implies that processes other than dry and wet deposition play a crucial role. The likeliest process responsible for enriching the concentration of insoluble snowpack impurities in surface snow is that the impurities not flushed away in meltwater remain behind in the unmelted snow Sterle et al, 2013;Xu et al, 2012).…”

Section: Deposition Variability Of Bc Oc and Dustmentioning

confidence: 99%

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Climate effect of black carbon aerosol in a Tibetan Plateau glacier

Song

Cao

et al. 2015

Atmospheric Environment

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h i g h l i g h t sWe sampled surface snow and snow pits in the snowmelt season in a Tibetan glacier. We depicted the variability of BC, OC, and dust concentrations. Scavenging efficiency and enrichment for BC and OC were derived. We evaluated BC radiative forcing in snow using SNICAR. a r t i c l e i n f o a b s t r a c tIn the Tibetan Plateau, the black carbon (BC) concentration in surface snow and snow pits has received much attention, whereas the seasonal behavior of aerosol-in-snow concentration, vertical profile, meltscavenging, and enrichment have received relatively little attention. Here we investigate these processes and their impacts on radiative forcing on the Muji glacier in the westernmost Tibetan Plateau during the 2012 snowmelt season. Increasing impurity concentrations were mostly due to post-deposition effects rather than new deposition. On 5 July, BC concentrations in the surface snow were higher than those of fresh snow, implying enrichment via sublimation and/or melting of previous snow. Fresh snow contained 25 ng g À1 BC on 27 July; afterward, BC gradually increased, reaching 730.6 ng g À1 in September. BC, organic carbon (OC), and dust concentrations co-varied but differed in magnitude. Melt-scavenging efficiencies were estimated at 0.19 ± 0.05 and 0.04 ± 0.01 for OC and BC, respectively, and the BC in surface snow increased by 20e25 times depending on melt intensity. BC-in-snow radiative forcing (RF) was approximately 2.2 W m À2 for fresh snow and 18.1e20.4 W m À2 for aged snow, and was sometimes reduced by the presence of dust.

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“…However, until now observations of BC in seasonal snow at mid-latitudes have been limited to studies focusing on a few sites in North America [Clarke and Noone, 1985;Chýlek et al, 1987;Cadle and Dasch, 1988;Dasch and Cadle, 1989], Europe [Sergent et al, 1993[Sergent et al, , 1998Fily et al, 1997;Armalis, 1999], and on glaciers in Tibet [Xu et al, 2006[Xu et al, , 2009[Xu et al, , 2012Ming et al, 2008Ming et al, , 2009. Here we present measurements of BC and other light-absorbing particles in snow from 46 sites widely distributed across north-central and northeast China from January and February 2010.…”

Section: Introductionmentioning

confidence: 97%

Black carbon and other light‐absorbing impurities in snow across Northern China

2013

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Black carbon (BC), organic carbon (OC), and mineral dust (MD) are the most important light‐absorbing particulate impurities in snow. A field campaign was conducted in January and February 2010 to measure light‐absorbing particles in snow across northern China. About 400 snow samples were collected at 46 sites in six provinces. A spectrophotometer was used to separate snow particulate absorption by BC and non‐BC constituents, based on the different spectral dependences of their light absorption. Light absorption by MD is due to iron oxides, so iron concentration was determined by chemical analysis. Using assumed mass absorption efficiencies for BC, OC, and iron, the fractional contribution of each to total absorption was estimated. BC is a product of combustion and iron is associated with MD, but OC in snow can be associated with either combustion products deposited to snow or from soil mixed into snow. The lowest concentrations of BC were in the remote northeast on the border of Siberia, with a median concentration in surface snow of 117 ng g–1. South of this, in the industrial northeast, the median snow BC concentration was 1220 ng g–1. In the northeast, snow particulate light absorption was dominated by BC. Across the grassland of Inner Mongolia, OC, likely mostly from local soil, dominates light absorption, with median BC concentrations of 340 ng g–1 responsible for only about one third of total particulate light absorption. In the Qilian Mountains, at the northern boundary of the Tibetan Plateau, snow particulate light absorption is dominated by local soil and desert dust.

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Post-depositional enrichment of black soot in snow-pack and accelerated melting of Tibetan glaciers

Cited by 124 publications

References 26 publications

An AeroCom assessment of black carbon in Arctic snow and sea ice

An AeroCom assessment of black carbon in Arctic snow and sea ice

Climate effect of black carbon aerosol in a Tibetan Plateau glacier

Black carbon and other light‐absorbing impurities in snow across Northern China

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