Light-absorbing impurities in Arctic snow

Doherty, Sarah J.; Warren, Stephen G.; Grenfell, Thomas C.; Clarke, A. D.; Brandt, Richard E.

doi:10.5194/acp-10-11647-2010

Cited by 451 publications

(810 citation statements)

References 98 publications

(152 reference statements)

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“…These relatively high values could be due to previous sublimation or melt (Doherty et al, 2010). On 10 July, much higher BC concentrations were consistent with rapid BC enrichment once the snow began to melt.…”

Section: Spatio-temporal Variability In Surface Snow Bcmentioning

confidence: 57%

“…Huang et al (2011) showed BC-in-snow concentrations decrease rapidly towards the northeast and away from major industrial regions. In the Arctic, Doherty et al (2010) and Forsstrom et al (2013) showed that the spatial differences in BC depended on the emission source intensity, the distance from the source to the deposition region, and the prevailing wind direction. In the eastern Sierra Nevada, Sterle et al (2013) noted that BC concentrations in aged snow were enhanced seven-fold relative to those in fresh snow.…”

Section: Introductionmentioning

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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Section: Spatio-temporal Variability In Surface Snow Bcmentioning

confidence: 57%

Section: Introductionmentioning

confidence: 99%

Climate effect of black carbon aerosol in a Tibetan Plateau glacier

Song

Cao

et al. 2015

Atmospheric Environment

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“…Previous studies have reported visible light absorption by non-BC particles (Yang et al 2009;Doherty et al 2010;Lack et al 2013). Doherty et al (2010) estimated that between 20% and 50% of the light absorption by particles in snowpack is caused by organic ("brown") carbon and dust.…”

Section: Uv/vis Spectrophotometermentioning

confidence: 99%

Measuring Organic Carbon and Black Carbon in Rainwater: Evaluation of Methods

Torres

Bond

Lehmann

et al. 2014

Aerosol Science and Technology

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Measuring wet deposition of organic carbon (OC) and black carbon (BC) is crucial for the complete understanding of the global circulation, lifetime, and radiative forcing of these aerosols. There is currently no accepted standard analytical method for measuring OC and BC concentration in precipitation. Different analytical methods have been employed for this purpose, but their feasibility has yet to be assessed. This manuscript evaluates the use of thermaloptical analysis (TOA), single-particle soot photometry (SP2), and ultraviolet-visible (UV/VIS) spectrophotometry for measuring BC in precipitation. In addition, total organic carbon (TOC) analysis was evaluated for the measurement of dissolved organic carbon (DOC) in precipitation. Potential interferences and sources of bias were assessed for each method. Precipitation samples and reference materials containing carbon particles generated from wood combustion and a natural gas diffusion flame were used in this study. The UV/VIS spectrophotometer, despite showing linearity with BC concentration, had inadequate sensitivity (±18 μg/L) to measure the low concentrations expected in precipitation. The SP2 analysis was adequate to measure refractory BC in precipitation in terms of precision and detection limit; however, systematic loss was estimated to be 34% (±3%). Sample filtration followed by TOA was inefficient for measuring particulate carbon in rainwater, as the quartz fiber filter captured less than 38% of the BC mass. Filtration was improved by adding salts and acids into the water samples, and ammonium dihydrogen phosphate, (NH 4 )H 2 PO 4 , was determined to be the best additive by increasing the collection efficiency of quartz fiber filters up to 95% (±5%). The TOC analyzer proved to be precise in the expected concentration range (200-5000 μg-C/L) for measuring DOC and total carbon (TC), including particulate OC and 94% (±2%) of the refractory BC in solution.

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“…They probably evolved under natural selection to actively melt snow, thereby generating needed liquid in a frozen environment. Snow algae contrast with episodic deposition of non-living particulates, which sink into the snowpack if hydrophilic or non-polar, and remain atop a single season's melting snowpack if hydrophobic 33,34 . Because algae remain on the surface over much of the melt season and perennially resurface across melt seasons, they compound their effects over time.…”

Section: Implications For High-latitude Ice Sheetsmentioning

confidence: 99%

The role of microbes in snowmelt and radiative forcing on an Alaskan icefield

et al. 2017

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A lack of liquid water limits life on glaciers worldwide but specialized microbes still colonize these environments. These microbes reduce surface albedo, which, in turn, could lead to warming and enhanced glacier melt. Here we present results from a replicated, controlled field experiment to quantify the impact of microbes on snowmelt in red-snow communities. Addition of nitrogen-phosphorous-potassium fertilizer increased alga cell counts nearly fourfold, to levels similar to nitrogen-phosphorusenriched lakes; water alone increased counts by half. The manipulated alga abundance explained a third of the observed variability in snowmelt. Using a normalized-di erence spectral index we estimated alga abundance from satellite imagery and calculated microbial contribution to snowmelt on an icefield of 1,900 km 2 . The red-snow area extended over about 700 km 2 , and in this area we determined that microbial communities were responsible for 17% of the total snowmelt there. Our results support hypotheses that snow-dwelling microbes increase glacier melt directly in a bio-geophysical feedback by lowering albedo and indirectly by exposing low-albedo glacier ice. Radiative forcing due to perennial populations of microbes may match that of non-living particulates at high latitudes. Their contribution to climate warming is likely to grow with increased melt and nutrient input.G lacier ablation is sensitive to changes in albedo 1 , with atmospheric 2,3 , hydrological 4 and ecological 5,6 consequences. Fresh snow reflects >90% of visible radiation, but during melt its grain size and water content increase, reducing albedo and further increasing snowmelt 1 . Impurities, including black carbon 3 , dust 4 , and resident microbes [7][8][9][10][11][12][13][14][15][16][17][18][19] , also lower albedo; however, microbes differ from non-living particulates in several critical ways. Perennial populations of photosynthetic microbes actively resurface following overwinter burial by snow 20 , and depend on liquid water and nutrients for survival and reproduction 13,14,[20][21][22] . This requirement for liquid water in a frozen environment imposes a selective force favouring a physiology that increases melt proximal to cell walls. The generation of meltwater through microbes' albedoreducing properties motivates an hypothesis of bio-geophysical feedback on glacial landscapes 13,16 , such as the Greenland ice sheet. This feedback hypothesis, whereby microbes increase because they produce needed meltwater, is an active research area [13][14][15][16][17][18][19] , yet field experiments testing its assumptions are absent.Glacier microbiomes are water-limited 21,22 , because ice is generally not metabolically available, and oligotrophic, because their nutrient content equals that of precipitation plus deposition by airborne dust, pollen, and so on, with only limited N-fixation by local cyanobacteria 21,22 . Moreover, rapidly percolating water through large-grained snow may exacerbate both water-and nutrient limitation for algae in supraglacial...

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Light-absorbing impurities in Arctic snow

Cited by 451 publications

References 98 publications

Climate effect of black carbon aerosol in a Tibetan Plateau glacier

Climate effect of black carbon aerosol in a Tibetan Plateau glacier

Measuring Organic Carbon and Black Carbon in Rainwater: Evaluation of Methods

The role of microbes in snowmelt and radiative forcing on an Alaskan icefield

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