Search for: All records

Abstract Natural aerosols are an important, yet understudied, part of the Arctic climate system. Natural marine biogenic aerosol components (e.g., methanesulfonic acid, MSA) are becoming increasingly important due to changing environmental conditions. In this study, we combine in situ aerosol observations with atmospheric transport modeling and meteorological reanalysis data in a data-driven framework with the aim to (1) identify the seasonal cycles and source regions of MSA, (2) elucidate the relationships between MSA and atmospheric variables, and (3) project the response of MSA based on trends extrapolated from reanalysis variables and determine which variables are contributing to these projected changes. We have identified the main source areas of MSA to be the Atlantic and Pacific sectors of the Arctic. Using gradient-boosted trees, we were able to explain 84% of the variance and find that the most important variables for MSA are indirectly related to either the gas- or aqueous-phase oxidation of dimethyl sulfide (DMS): shortwave and longwave downwelling radiation, temperature, and low cloud cover. We project MSA to undergo a seasonal shift, with non-monotonic decreases in April/May and increases in June-September, over the next 50 years. Different variables in different months are driving these changes, highlighting the complexity of influences on this natural aerosol component. Although the response of MSA due to changing oceanic variables (sea surface temperature, DMS emissions, and sea ice) and precipitation remains to be seen, here we are able to show that MSA will likely undergo a seasonal shift solely due to changes in atmospheric variables. 

Data availability pending. The Arctic is warming faster than any other place on Earth, with sea ice declining rapidly and sources of sea spray and biogenic aerosol emissions changing by consequence. Utqiagvik is at the forefront of this change, abutting one of the largest areas of sea ice loss. This change will have far-reaching impacts to both the environment and the community. Because this change has happened largely in the last decade, now is an important time to both document that change and to continue a data record that will allow for a characterization of the New Arctic, as climate is already altering the Arctic landscape forever. The longest and most complete record of aerosol properties in the American Arctic is that of Utqiagvik, making this unique location serve as a regional record of changes in atmospheric aerosol properties. This dataset will extend the baseline measurements of this Arctic aerosol record, including and continuing the 15-year record of submicron inorganic components (Quinn et al., 2009; Quinn et al., 2002), re-instituting the 2-year record of organic components collected a decade ago (Frossard et al., 2011; Shaw et al., 2010), enhancing the chemical analysis with sulfur isotopes to improve interpretation of emission sources (Kunasek et al., 2010; Thiemens & Lin, 2019), continuing particle number size distribution measurements (Freud et al., 2017), and re-starting cloud condensation nuclei measurements (Schmale, Henning, et al., 2018). 

### Access Dataset and extensive metadata can be accessed and downloaded from the 'ADC' directory via: [http://arcticdata.io/data/10.18739/A2X05XF2D](http://arcticdata.io/data/10.18739/A2X05XF2D) ### Overview The Arctic is warming faster than any other place on Earth, with sea ice declining rapidly and sources of sea spray and biogenic aerosol emissions changing by consequence. Utqiagvik is at the forefront of this change, abutting one of the largest areas of sea ice loss. This change will have far-reaching impacts to both the environment and the community. Because this change has happened largely in the last decade, now is an important time to both document that change and to continue a data record that will allow for a characterization of the New Arctic, as climate is already altering the Arctic landscape forever. The longest and most complete record of aerosol properties in the American Arctic is that of Utqiagvik, making this unique location serve as a regional record of changes in atmospheric aerosol properties. This dataset will extend the baseline measurements of this Arctic aerosol record, including and continuing the 15-year record of submicron inorganic components (Quinn et al., 2009; Quinn et al., 2002), re-instituting the 2-year record of organic components collected a decade ago (Frossard et al., 2011; Shaw et al., 2010), enhancing the chemical analysis with sulfur isotopes to improve interpretation of emission sources (Kunasek et al., 2010; Thiemens & Lin, 2019), continuing particle number size distribution measurements (Freud et al., 2017), and re-starting cloud condensation nuclei measurements (Schmale, Henning, et al., 2018). 

### Access Dataset can be accessed and downloaded from the 'ADC' directory via: [http://arcticdata.io/data/10.18739/A2X63B701](http://arcticdata.io/data/10.18739/A2X63B701) ### Overview The Arctic is warming faster than any other place on Earth, with sea ice declining rapidly and sources of sea spray and biogenic aerosol emissions changing by consequence. Utqiagvik is at the forefront of this change, abutting one of the largest areas of sea ice loss. This change will have far-reaching impacts to both the environment and the community. Because this change has happened largely in the last decade, now is an important time to both document that change and to continue a data record that will allow for a characterization of the New Arctic, as climate is already altering the Arctic landscape forever. The longest and most complete record of aerosol properties in the American Arctic is that of Utqiagvik, making this unique location serve as a regional record of changes in atmospheric aerosol properties. This dataset will extend the baseline measurements of this Arctic aerosol record, including and continuing the 15-year record of submicron inorganic components (Quinn et al., 2009; Quinn et al., 2002), re-instituting the 2-year record of organic components collected a decade ago (Frossard et al., 2011; Shaw et al., 2010), enhancing the chemical analysis with sulfur isotopes to improve interpretation of emission sources (Kunasek et al., 2010; Thiemens & Lin, 2019), continuing particle number size distribution measurements (Freud et al., 2017), and re-starting cloud condensation nuclei measurements (Schmale, Henning, et al., 2018). 

Anthropogenic and natural emissions contribute to enhanced concentrations of aerosols in the Arctic winter and early spring, with most attention being paid to anthropogenic aerosols that contribute to so-called Arctic haze. Less-well-studied wintertime sea-spray aerosols (SSAs) under Arctic haze conditions are the focus of this study, since they can make an important contribution to wintertime Arctic aerosol abundances. Analysis of field campaign data shows evidence for enhanced local sources of SSAs, including marine organics at Utqiaġvik (formerly known as Barrow) in northern Alaska, United States, during winter 2014. Models tend to underestimate sub-micron SSAs and overestimate super-micron SSAs in the Arctic during winter, including the base version of the Weather Research Forecast coupled with Chemistry (WRF-Chem) model used here, which includes a widely used SSA source function based on Gong et al. (1997). Quasi-hemispheric simulations for winter 2014 including updated wind speed and sea-surface temperature (SST) SSA emission dependencies and sources of marine sea-salt organics and sea-salt sulfate lead to significantly improved model performance compared to observations at remote Arctic sites, notably for coarse-mode sodium and chloride, which are reduced. The improved model also simulates more realistic contributions of SSAs to inorganic aerosols at different sites, ranging from 20 %–93 % in the observations. Two-thirds of the improved model performance is from the inclusion of the dependence on SSTs. The simulation of nitrate aerosols is also improved due to less heterogeneous uptake of nitric acid on SSAs in the coarse mode and related increases in fine-mode nitrate. This highlights the importance of interactions between natural SSAs and inorganic anthropogenic aerosols that contribute to Arctic haze. Simulation of organic aerosols and the fraction of sea-salt sulfate are also improved compared to observations. However, the model underestimates episodes with elevated observed concentrations of SSA components and sub-micron non-sea-salt sulfate at some Arctic sites, notably at Utqiaġvik. Possible reasons are explored in higher-resolution runs over northern Alaska for periods corresponding to the Utqiaġvik field campaign in January and February 2014. The addition of a local source of sea-salt marine organics, based on the campaign data, increases modelled organic aerosols over northern Alaska. However, comparison with previous available data suggests that local natural sources from open leads, as well as local anthropogenic sources, are underestimated in the model. Missing local anthropogenic sources may also explain the low modelled (sub-micron) non-sea-salt sulfate at Utqiaġvik. The introduction of a higher wind speed dependence for sub-micron SSA emissions, also based on Arctic data, reduces biases in modelled sub-micron SSAs, while sea-ice fractions, including open leads, are shown to be an important factor controlling modelled super-micron, rather than sub-micron, SSAs over the north coast of Alaska. The regional results presented here show that modelled SSAs are more sensitive to wind speed dependence but that realistic modelling of sea-ice distributions is needed for the simulation of local SSAs, including marine organics. This study supports findings from the Utqiaġvik field campaign that open leads are the primary source of fresh and aged SSAs, including marine organic aerosols, during wintertime at Utqiaġvik; these findings do not suggest an influence from blowing snow and frost flowers. To improve model simulations of Arctic wintertime aerosols, new field data on processes that influence wintertime SSA production, in particular for fine-mode aerosols, are needed as is improved understanding about possible local anthropogenic sources. 

Marine cloud brightening (MCB) is the deliberate injection of aerosol particles into shallow marine clouds to increase their reflection of solar radiation and reduce the amount of energy absorbed by the climate system. From the physical science perspective, the consensus of a broad international group of scientists is that the viability of MCB will ultimately depend on whether observations and models can robustly assess the scale-up of local-to-global brightening in today’s climate and identify strategies that will ensure an equitable geographical distribution of the benefits and risks associated with projected regional changes in temperature and precipitation. To address the physical science knowledge gaps required to assess the societal implications of MCB, we propose a substantial and targeted program of research—field and laboratory experiments, monitoring, and numerical modeling across a range of scales. 

The number concentration and properties of aerosol particles serving as cloud condensation nuclei (CCN) are important for understanding cloud properties, including in the tropical Atlantic marine boundary layer (MBL), where marine cumulus clouds reflect incoming solar radiation and obscure the low-albedo ocean surface. Studies linking aerosol source, composition, and water uptake properties in this region have been conducted primarily during the summertime dust transport season, despite the region receiving a variety of aerosol particle types throughout the year. In this study, we compare size-resolved aerosol chemical composition data to the hygrocopicity parameter κ derived from size-resolved CCN measurements made during the Elucidating the Role of Clouds-Circulation Coupling in Climate (EUREC4A) and Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC) campaigns from January to February 2020. We observed unexpected periods of wintertime long-range transport of African smoke and dust to Barbados. During these periods, the accumulation-mode aerosol particle and CCN Number concentrations as well as the proportions of dust and smoke particles increased, whereas average κ slightly decreased (κ = 0.46 +/- 0.10) from marine background conditions (κ = 0.52 +/- 0.09) when the particles were mostly composed of marine organics and sulfate. Size-resolved chemical analysis shows that smoke particles were the major contributor to the accumulation mode during long-range transport events, indicating that smoke is mainly responsible for the observed increase in CCN number concentrations. Earlier studies conducted at Barbados have mostly focused on the role of dust in CCN, but our results show that aerosol hygroscopicity and CCN number concentrations during wintertime long-range transport events over the tropical North Atlantic are also affected by African smoke. Our findings highlight the importance of African smoke for atmospheric processes and cloud formation over the Caribbean. In the file “Dust_Mass_Conc_Royer2022” dust mass concentrations in grams per meter^3 are provided for each day of sampling. These data were used to generate Figure 2a in the manuscript. The file “Particle_Type_#fract_Royer2022” contains data obtained through CCSEM/EDX analysis and used to generate the temporal chemistry plot (Figure 4) provided in the manuscript. The data contains particle numbers for each particle type identified on stage 3 of the sampler, total particle numbers analyzed for the entire stage 3 sample, as well as particle number fractions in % values. In the file “Size-resolved_chem_Royer2022” we provide particle # and number fraction (%) values used to generate size-resolved chemistry plots in the manuscript (Figures 5a and 5b). The file includes all particle numbers and number fractions for sea salt, aged sea salt, dust+sea salt, dust, dust+smoke, smoke, sulfate, and organic particles in each size bin from 0.1 through 8.058 um during cumulative clean marine periods and CAT Event 1 as described in the manuscript. The file “K_at_0.16S_Royer2022” contains κ values calculated at 0.16% supersaturation (S) throughout the entire sampling period. These data were specifically used to generate the plot in Figure 7a. The file “CCN#_at_0.16S_Royer2022” contains cloud condensation nuclei (CCN) values calculated at 0.16% supersaturation (S) throughout the entire sampling period. These data were used to create the CCN portion of the plot in Figure 7b. 

Abstract. The number concentration and properties of aerosol particles serving ascloud condensation nuclei (CCN) are important for understanding cloudproperties, including in the tropical Atlantic marine boundary layer (MBL), where marine cumulus clouds reflect incoming solar radiation and obscure thelow-albedo ocean surface. Studies linking aerosol source, composition, andwater uptake properties in this region have been conducted primarily duringthe summertime dust transport season, despite the region receiving a varietyof aerosol particle types throughout the year. In this study, we comparesize-resolved aerosol chemical composition data to the hygroscopicityparameter κ derived from size-resolved CCN measurements made duringthe Elucidating the Role of Clouds–Circulation Coupling in Climate (EUREC4A) and Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC) campaigns from January to February 2020. Weobserved unexpected periods of wintertime long-range transport of Africansmoke and dust to Barbados. During these periods, the accumulation-mode aerosol particle and CCN number concentrations as well as the proportions ofdust and smoke particles increased, whereas the average κ slightlydecreased (κ=0.46±0.10) from marine backgroundconditions (κ=0.52±0.09) when the submicron particles were mostly composed of marine organics and sulfate. Size-resolved chemicalanalysis shows that smoke particles were the major contributor to theaccumulation mode during long-range transport events, indicating that smokeis mainly responsible for the observed increase in CCN numberconcentrations. Earlier studies conducted at Barbados have mostly focused onthe role of dust on CCN, but our results show that aerosol hygroscopicity and CCN number concentrations during wintertime long-range transport events over the tropical North Atlantic are also affected by African smoke. Ourfindings highlight the importance of African smoke for atmospheric processesand cloud formation over the Caribbean.