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

2014 ◽  
Vol 14 (5) ◽  
pp. 2399-2417 ◽  
Author(s):  
C. Jiao ◽  
M. G. Flanner ◽  
Y. Balkanski ◽  
S. E. Bauer ◽  
N. Bellouin ◽  
...  
Keyword(s):  
Sea Ice ◽  
Phase I ◽  
Black Carbon ◽  
Phase Ii ◽  
Full Range ◽  
Deposition Efficiency ◽  
The Arctic ◽  
Radiative Effect ◽  
Field Campaign ◽  
Scavenging Efficiency

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 −4.4 (−13.2 to +10.7) ng g−1 for an earlier phase of AeroCom models (phase I), and +4.1 (−13.0 to +21.4) ng g−1 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.

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

2013 ◽  
Vol 13 (10) ◽  
pp. 26217-26267 ◽  
Author(s):  
C. Jiao ◽  
M. G. Flanner ◽  
Y. Balkanski ◽  
S. E. Bauer ◽  
N. Bellouin ◽  
...  
Keyword(s):  
Sea Ice ◽  
Phase I ◽  
Black Carbon ◽  
Phase Ii ◽  
Full Range ◽  
Deposition Efficiency ◽  
The Arctic ◽  
Radiative Effect ◽  
Field Campaign ◽  
Scavenging Efficiency

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 2004–2009, 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 –4.4 (–13.2 to +10.7) ng g−1 for an earlier Phase of AeroCom models (Phase I), and +4.1 (–13.0 to +21.4) ng g−1 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.

scholarly journals Brief communication: An alternative method for estimating the scavenging efficiency of black carbon by meltwater over sea ice

2019 ◽  
Vol 13 (12) ◽  
pp. 3309-3316
Author(s):  
Tingfeng Dou ◽  
Zhiheng Du ◽  
Shutong Li ◽  
Yulan Zhang ◽  
Qi Zhang ◽  
...  
Keyword(s):  
Surface Layer ◽  
Sea Ice ◽  
Black Carbon ◽  
Large Scale ◽  
Chukchi Sea ◽  
The Arctic ◽  
Observation Area ◽  
Scavenging Efficiency ◽  
Crucial Parameter ◽  
Melting Season

Abstract. The meltwater scavenging coefficient (MSC) of black carbon (BC) is a crucial parameter in snow and sea ice models, as it determines the BC enrichment in the surface layer of melting snow over sea ice and therefore modulates the BC–snow–albedo feedbacks. We present a new method for MSC estimation by sampling the melt–refreeze ice layer that is produced from refreezing of the meltwater within snowpack and its overlying snow and measuring their physical characteristics in Elson Lagoon northeast of Utqiaġvik (formerly Barrow), Alaska, during the melting season. The bias of estimated MSC ranges from −5.4 % to 7.3 %, which is not exactly dependent on the degree of ablation. The average MSC value calculated with this proposed method is slightly lower than that derived from the repeating sampling (RS) method in Elson Lagoon while still being within its best estimate range. Further estimation demonstrates that the MSC in the Canada Basin (23.6 %±2.1 %) is close to that in Greenland (23.0 %±12.5 %) and larger than that in the Chukchi Sea (17.9 %±5.0 %) in the northwest of Utqiaġvik. Elson Lagoon has the lowest MSC (14.5 %±2.6 %) in the study areas. The method suggested in this study provides a possible approach for large-scale measurements of MSC over the sea ice area in the Arctic. Of course, this method depends on the presence of a melt–refreeze ice layer in the observation area.

scholarly journals Factors Controlling Black Carbon Distribution in the Arctic

2016 ◽  
Author(s):  
Ling Qi ◽  
Qinbin Li ◽  
Yingrui Li ◽  
Cenlin He
Keyword(s):  
Black Carbon ◽  
Dry Deposition ◽  
Model Simulation ◽  
Deposition Velocity ◽  
Mixed Phase ◽  
The Arctic ◽  
Dry Deposition Velocity ◽  
Mixed Phase Clouds ◽  
Scavenging Efficiency ◽  
Snow And Ice

Abstract. We investigate the sensitivity of black carbon (BC) in the Arctic, including BC in snow (BCsnow, ng g−1) and surface air (BCair, μg m−3), to emissions, dry deposition and wet scavenging using a global 3-D chemical transport model (CTM) GEOS-Chem. We find that the model underestimates BCsnow in the Arctic by 40 % on average (median = 11.8 ng g−1). Natural gas flaring substantially increases total BC emissions in the Arctic (by ~ 70 %). The flaring emissions lead to up to 49 % increases (0.1–8.5 ng g−1) in Arctic BCsnow, dramatically improving model comparison with observations (50 % reduction in discrepancy) near flaring source regions (Western Extreme North of Russia). Ample observations suggest that BC dry deposition velocities over snow and ice in current CTMs (0.03 cm s−1 in GEOS-Chem) are exceedingly small. We apply the resistance-in-series method to compute the dry deposition velocity that varies with local meteorological and surface conditions. The resulting velocity is significantly larger and varies by a factor of eight in the Arctic (0.03–0.24 cm s−1), increases the fraction of dry to total BC deposition (16 % to 25 %), yet leaves the total BC deposition and BCsnow in the Arctic unchanged. This is largely explained by the offsetting higher dry and lower wet deposition fluxes. Additionally, we account for the effect of the Wegener-Bergeron-Findeisen (WBF) process in mixed-phase clouds, which releases BC particles from condensed phases (water drops and ice crystals) back to the interstitial air and thereby substantially reduces the scavenging efficiency of BC (by 43–76 % in the Arctic). The resulting BCsnow is up to 80 % higher, BC loading is considerably larger (from 0.25 to 0.43 mg  m−2), and BC lifetime is markedly prolonged (from 9 to 16 days) in the Arctic. Over all, flaring emissions increase BCair in the Arctic (by ~ 20 ng m−3), the updated dry deposition velocity more than halves BCair (by ~ 20 ng  m−3), and the WBF effect increases BCair by 25–70 % during winter and early spring. The resulting model simulation of BCsnow is substantially improved (within 10 % of the observations) and the discrepancies of BCair are much smaller during snow season at Barrow, Alert and Summit (from −67 %–−47 % to −46 %–3 %). Our results point toward an urgent need for better characterization of flaring emissions of BC (e.g. the emission factors, temporal and spatial distribution), extensive measurements of both the dry deposition of BC over snow and ice, and the scavenging efficiency of BC in mixed-phase clouds.

scholarly journals Contrasting source contributions of Arctic black carbon to atmospheric concentrations, deposition flux, and atmospheric and snow radiative effects

2022 ◽  
Author(s):  
Hitoshi Matsui ◽  
Tatsuhiro Mori ◽  
Sho Ohata ◽  
Nobuhiro Moteki ◽  
Naga Oshima ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Black Carbon ◽  
Seasonal Variations ◽  
Climate Impacts ◽  
The Arctic ◽  
Deposition Flux ◽  
Radiative Effect ◽  
Radiative Effects ◽  
Source Contributions ◽  
Mass Concentrations

Abstract. Black carbon (BC) particles in the Arctic contribute to rapid warming of the Arctic by heating the atmosphere and snow and ice surfaces. Understanding the source contributions to Arctic BC is therefore important, but they are not well understood, especially those for atmospheric and snow radiative effects. Here we estimate simultaneously the source contributions of Arctic BC to near-surface and vertically integrated atmospheric BC mass concentrations (MBC_SRF and MBC_COL), BC deposition flux (MBC_DEP), and BC radiative effects at the top of the atmosphere and snow surface (REBC_TOA and REBC_SNOW), and show that the source contributions to these five variables are highly different. In our estimates, Siberia makes the largest contribution to MBC_SRF, MBC_DEP, and REBC_SNOW in the Arctic (defined as > 70° N), accounting for 70 %, 53 %, and 43 %, respectively. In contrast, Asia’s contributions to MBC_COL and REBC_TOA are largest, accounting for 38 % and 45 %, respectively. In addition, the contributions of biomass burning sources are larger (24−34 %) to MBC_DEP, REBC_TOA, and REBC_SNOW, which are highest from late spring to summer, and smaller (4.2−14 %) to MBC_SRF and MBC_COL, whose concentrations are highest from winter to spring. These differences in source contributions to these five variables are due to seasonal variations in BC emission, transport, and removal processes and solar radiation, as well as to differences in radiative effect efficiency (radiative effect per unit BC mass) among sources. Radiative effect efficiency varies by a factor of up to 4 among sources (1465−5439 W g–1) depending on lifetimes, mixing states, and heights of BC and seasonal variations of emissions and solar radiation. As a result, source contributions to radiative effects and mass concentrations (i.e., REBC_TOA and MBC_COL, respectively) are substantially different. The results of this study demonstrate the importance of considering differences in the source contributions of Arctic BC among mass concentrations, deposition, and atmospheric and snow radiative effects for accurate understanding of Arctic BC and its climate impacts.

The dawn of Molecular Genetics in Paleoceanography: tracing Arctic change during the Holocene with marine sedaDNA records from Greenland

2020 ◽  
Author(s):  
Sofia Ribeiro ◽  
Sara Hardardottir ◽  
Jessica Louise Ray ◽  
Stijn De Schepper ◽  
Audrey Limoges ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Full Range ◽  
Sediment Cores ◽  
Critical Role ◽  
Genetic Material ◽  
Digital Pcr ◽  
The Arctic ◽  
Taxonomic Resolution ◽  
Gene Copy

<p>As we move towards a “blue” Arctic Ocean in the summer within the next decades, predicting the full range of effects of climate change on the marine arctic environment remains a challenge. This is partly due to the paucity of long-term data on ocean-biosphere-cryosphere interactions over time and partly because, today, much of our knowledge on past ocean variability derives from microfossil and biogeochemical tracers that all have considerable limitations such as preservation biases and low taxonomic resolution or coverage.</p><p>Recent studies have revealed sedaDNA as a potential “game-changer” in our ability to reconstruct past ocean conditions, due to the preservation of DNA at low temperatures, and the possibility to capture a much larger fraction of the Arctic marine biome diversity than with classical approaches. However, while sedaDNA has been used in terrestrial, archeological, and lake studies for some years, its application to marine sediment records is still in its infancy.</p><p>Here, we will present new results from material recently collected along the two Arctic Ocean outflow shelves off Greenland (Greenland Sea/Fram Strait and Northern Baffin Bay/Nares Strait). We have used a combination of modern and ancient DNA methods applied to seawater, surface sediments, and sediment cores covering the past ca. 12 000 years with the objectives of: 1) characterizing the vertical export of sea ice-associated genetic material through the water column and into the sediments following sea ice melt and 2) exploring the potential of sedaDNA from the circum-polar sea ice dinoflagellate Polarella glacialis as a new sea ice proxy. For the first objective, we followed a comparative metabarcoding approach while the second objective included designing species-specific primers followed by gene copy number quantification by a droplet digital PCR assay. </p><p>We argue that sedaDNA will have a critical role in expanding the Paleoceanography “toolbox” and lead to the establishment of a new cross-disciplinary field.</p><p> </p>

scholarly journals Effects of the Wegener–Bergeron–Findeisen process on global black carbon distribution

2017 ◽  
Vol 17 (12) ◽  
pp. 7459-7479 ◽  
Author(s):  
Ling Qi ◽  
Qinbin Li ◽  
Cenlin He ◽  
Xin Wang ◽  
Jianping Huang
Keyword(s):  
Black Carbon ◽  
Transport Model ◽  
Mixed Phase ◽  
The Arctic ◽  
Deposition Flux ◽  
Chemical Transport Model ◽  
Washout Ratio ◽  
Cloud Scavenging ◽  
Mixed Phase Clouds ◽  
Scavenging Efficiency

Abstract. We systematically investigate the effects of Wegener–Bergeron–Findeisen process (hereafter WBF) on black carbon (BC) scavenging efficiency, surface BCair, deposition flux, concentration in snow (BCsnow, ng g−1), and washout ratio using a global 3-D chemical transport model (GEOS-Chem). We differentiate riming- versus WBF-dominated in-cloud scavenging based on liquid water content (LWC) and temperature. Specifically, we implement an implied WBF parameterization using either temperature or ice mass fraction (IMF) in mixed-phase clouds based on field measurements. We find that at Jungfraujoch, Switzerland, and Abisko, Sweden, where WBF dominates in-cloud scavenging, including the WBF effect strongly reduces the discrepancies of simulated BC scavenging efficiency and washout ratio against observations (from a factor of 3 to 10 % and from a factor of 4–5 to a factor of 2). However, at Zeppelin, Norway, where riming dominates, simulation of BC scavenging efficiency, BCair, and washout ratio become worse (relative to observations) when WBF is included. There is thus an urgent need for extensive observations to distinguish and characterize riming- versus WBF-dominated aerosol scavenging in mixed-phase clouds and the associated BC scavenging efficiency. Our model results show that including the WBF effect lowers global BC scavenging efficiency, with a higher reduction at higher latitudes (8 % in the tropics and up to 76 % in the Arctic). The resulting annual mean BCair increases by up to 156 % at high altitudes and at northern high latitudes because of lower temperature and higher IMF. Overall, WBF halves the model–observation discrepancy (from −65 to −30 %) of BCair across North America, Europe, China and the Arctic. Globally WBF increases BC burden from 0.22 to 0.29–0.35 mg m−2 yr−1, which partially explains the gap between observed and previous model-simulated BC burdens over land. In addition, WBF significantly increases BC lifetime from 5.7 to  ∼  8 days. Additionally, WBF results in a significant redistribution of BC deposition in source and remote regions. Specifically, it lowers BC wet deposition (by 37–63 % at northern mid-latitudes and by 21–29 % in the Arctic), while it increases dry deposition (by 3–16 % at mid-latitudes and by 81–159 % in the Arctic). The resulting total BC deposition is lower at mid-latitudes (by 12–34 %) but higher in the Arctic (by 2–29 %). We find that WBF decreases BCsnow at mid-latitudes (by  ∼  15 %) but increases it in the Arctic (by 26 %) while improving model comparisons with observations. In addition, WBF dramatically reduces the model–observation discrepancy of washout ratios in winter (from a factor of 16 to 4). The remaining discrepancies in BCair, BCsnow and BC washout ratios suggest that in-cloud removal in mixed-phased clouds is likely still excessive over land.

scholarly journals Factors controlling black carbon distribution in the Arctic

2017 ◽  
Vol 17 (2) ◽  
pp. 1037-1059 ◽  
Author(s):  
Ling Qi ◽  
Qinbin Li ◽  
Yinrui Li ◽  
Cenlin He
Keyword(s):  
Black Carbon ◽  
Dry Deposition ◽  
Model Comparison ◽  
Model Simulation ◽  
Deposition Velocity ◽  
Mixed Phase ◽  
The Arctic ◽  
Mixed Phase Clouds ◽  
Scavenging Efficiency ◽  
Snow And Ice

Abstract. We investigate the sensitivity of black carbon (BC) in the Arctic, including BC concentration in snow (BCsnow, ng g−1) and surface air (BCair, ng m−3), as well as emissions, dry deposition, and wet scavenging using the global three-dimensional (3-D) chemical transport model (CTM) GEOS-Chem. We find that the model underestimates BCsnow in the Arctic by 40 % on average (median  =  11.8 ng g−1). Natural gas flaring substantially increases total BC emissions in the Arctic (by ∼ 70 %). The flaring emissions lead to up to 49 % increases (0.1–8.5 ng g−1) in Arctic BCsnow, dramatically improving model comparison with observations (50 % reduction in discrepancy) near flaring source regions (the western side of the extreme north of Russia). Ample observations suggest that BC dry deposition velocities over snow and ice in current CTMs (0.03 cm s−1 in the GEOS-Chem) are too small. We apply the resistance-in-series method to compute a dry deposition velocity (vd) that varies with local meteorological and surface conditions. The resulting velocity is significantly larger and varies by a factor of 8 in the Arctic (0.03–0.24 cm s−1), which increases the fraction of dry to total BC deposition (16 to 25 %) yet leaves the total BC deposition and BCsnow in the Arctic unchanged. This is largely explained by the offsetting higher dry and lower wet deposition fluxes. Additionally, we account for the effect of the Wegener–Bergeron–Findeisen (WBF) process in mixed-phase clouds, which releases BC particles from condensed phases (water drops and ice crystals) back to the interstitial air and thereby substantially reduces the scavenging efficiency of clouds for BC (by 43–76 % in the Arctic). The resulting BCsnow is up to 80 % higher, BC loading is considerably larger (from 0.25 to 0.43 mg m−2), and BC lifetime is markedly prolonged (from 9 to 16 days) in the Arctic. Overall, flaring emissions increase BCair in the Arctic (by ∼ 20 ng m−3), the updated vd more than halves BCair (by ∼ 20 ng m−3), and the WBF effect increases BCair by 25–70 % during winter and early spring. The resulting model simulation of BCsnow is substantially improved (within 10 % of the observations) and the discrepancies of BCair are much smaller during the snow season at Barrow, Alert, and Summit (from −67–−47 % to −46–3 %). Our results point toward an urgent need for better characterization of flaring emissions of BC (e.g., the emission factors, temporal, and spatial distribution), extensive measurements of both the dry deposition of BC over snow and ice, and the scavenging efficiency of BC in mixed-phase clouds. In addition, we find that the poorly constrained precipitation in the Arctic may introduce large uncertainties in estimating BCsnow. Doubling precipitation introduces a positive bias approximately as large as the overall effects of flaring emissions and the WBF effect; halving precipitation produces a similarly large negative bias.

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