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Bahramvash Shams, Shima, Von P. Walden, Irina Petropavlovskikh, David Tarasick, Rigel Kivi, Samuel Oltmans, Bryan Johnson, Patrick Cullis, Chance W. Sterling, Laura Thölix and Quentin Errera, (2019), Variations in the vertical profile of ozone at four high-latitude Arctic sites from 2005 to 2017, Atmospheric Chemistry and Physics, 19, 15, 9733-9751, 10.5194/acp-19-9733-2019

Abstract

Abstract. Understanding variations in atmospheric ozone in the Arctic is difficult because there are only a few long-term records of vertical ozone profiles in this region. We present 12 years of ozone profiles from February 2005 to February 2017 at four sites: Summit Station, Greenland; Ny-Ålesund, Svalbard, Norway; and Alert and Eureka, Nunavut, Canada. These profiles are created by combining ozonesonde measurements with ozone profile retrievals using data from the Microwave Limb Sounder (MLS). This combination creates a high-quality dataset with low uncertainty values by relying on in situ measurements of the maximum altitude of the ozonesondes (∼30 km) and satellite retrievals in the upper atmosphere (up to 60 km). For each station, the total column ozone (TCO) and the partial column ozone (PCO) in four atmospheric layers (troposphere to upper stratosphere) are analyzed. Overall, the seasonal cycles are similar at these sites. However, the TCO over Ny-Ålesund starts to decline 2 months later than at the other sites. In summer, the PCO in the upper stratosphere over Summit Station is slightly higher than at the other sites and exhibits a higher standard deviation. The decrease in PCO in the middle and upper stratosphere during fall is also lower over Summit Station. The maximum value of the lower- and middle-stratospheric PCO is reached earlier in the year over Eureka. Trend analysis over the 12-year period shows significant trends in most of the layers over Summit and Ny-Ålesund during summer and fall. To understand deseasonalized ozone variations, we identify the most important dynamical drivers of Arctic ozone at each level. These drivers are chosen based on mutual selected proxies at the four sites using stepwise multiple regression (SMR) analysis of various dynamical parameters with deseasonalized data. The final regression model is able to explain more than 80 % of the TCO and more than 70 % of the PCO in almost all of the layers. The regression model provides the greatest explanatory value in the middle stratosphere. The important proxies of the deseasonalized ozone time series at the four sites are tropopause pressure (TP) and equivalent latitude (EQL) at 370 K in the troposphere, the quasi-biennial oscillation (QBO) in the troposphere and lower stratosphere, the equivalent latitude at 550 K in the middle and upper stratosphere, and the eddy heat flux (EHF) and volume of polar stratospheric clouds throughout the stratosphere.

Bergin, M.H., C.I. Davidson, J.E. Dibb, J.L. Jaffrezo, H.D. Kuhns and S.N. Pandis, (1995), A simple model to estimate atmospheric concentrations of aerosol chemical species based on snow core chemistry at Summit, Greenland, Geophysical Research Letters, 22, 24, 3517-3520, 95GL03196

Abstract

A simple model is presented to estimate atmospheric concentrations of chemical species that exist primarily as aerosols based on snow core/ice core chemistry at Summit, Greenland. The model considers the processes of snow, fog, and dry deposition. The deposition parameters for each of the processes are estimated for SO4 2? and Ca2+ and are based on experiments conducted during the 1993 and 1994 summer field seasons. The seasonal mean atmospheric concentrations are estimated based on the deposition parameters and snow cores obtained during the field seasons. The ratios of the estimated seasonal mean airborne concentration divided by the measured mean concentration ( C ¯ a,est / C ¯ a,meas ) for SO4 2? over the 1993 and 1994 field seasons are 0.85 and 0.95, respectively. The C ¯ a,est / C ¯ a,meas ratios for Ca2+ are 0.45 and 0.90 for the 1993 and 1994 field seasons. The uncertainties in the estimated atmospheric concentrations range from 30% to 40% and are due to variability in the input parameters. The model estimates the seasonal mean atmospheric SO4 2? and Ca2+ concentrations to within 15% and 55%, respectively. Although the model is not directly applied to ice cores, the application of the model to ice core chemical signals is briefly discussed.
Bergin, M.H., J.-L. Jaffrezo, C.I. Davidson, J.E. Dibb, S.N. Pandis, R. Hillamo, W. Maenhaut, H.D. Kuhns and T. Makela, (1995), The contributions of snow, fog, and dry deposition to the summer flux of anions and cations at Summit, Greenland, Journal of Geophysical Research-Atmospheres, 100, D8, 16275-16288, 95JD01267

Abstract

Experiments were performed during the period May-July of 1993 at Summit, Greenland. Aerosol mass size distributions as well as daily average concentrations of several anionic and cationic species were measured. Dry deposition velocities for SO4 2? were estimated using surrogate surfaces (symmetric airfoils) as well as impactor data. Real-time concentrations of particles greater than 0.5 ?m and greater than 0.01 ?m were measured. Snow and fog samples from nearly all of the events occurring during the field season were collected. Filter sampler results indicate that SO4 2? is the dominant aerosol anion species, with Na+, NH4 +, and Ca2+ being the dominant cations. Impactor results indicate that MSA and SO4 2? have similar mass size distributions. Furthermore, MSA and SO4 2? have mass in both the accumulation and coarse modes. A limited number of samples for NH4 + indicate that it exists in the accumulation mode. Na, K, Mg, and Ca exist primarily in the coarse mode. Dry deposition velocities estimated from impactor samples and a theory for dry deposition to snow range from 0.017 cm/s +/? 0.011 cm/s for NH4 + to 0.110 cm/s +/? 0.021 cm/s for Ca. SO4 2? dry deposition velocity estimates using airfoils are in the range 0.023 cm/s to 0.062 cm/s, as much as 60% greater than values calculated using the airborne size distribution data. The rough agreement between the airfoil and impactor-estimated dry deposition velocities suggests that the airfoils may be used to approximate the dry deposition to the snow surface. Laser particle counter (LPC) results show that particles > 0.5 ?m in diameter efficiently serve as nuclei to form fog droplets. Condensation nuclei (CN) measurements indicate that particles < 0.5 ?m are not as greatly affected by fog. Furthermore, impactor measurements suggest that from 50% to 80% of the aerosol SO4 2? serves as nuclei for fog droplets. Snow deposition is the dominant mechanism transporting chemicals to the ice sheet. For NO3 ?, a species that apparently exists primarily in the gas phase as HNO3(g), 93% of the seasonal inventory (mass of a deposited chemical species per unit area during the season) is due to snow deposition, which suggests efficient scavenging of HNO3(g) by snowflakes. The contribution of snow deposition to the seasonal inventories of aerosols ranges from 45% for MSA to 76% for NH4 +. The contribution of fog to the seasonal inventories ranges from 13% for Na+ and Ca2+ to 26% and 32% for SO4 2? and MSA. The dry deposition contribution to the seasonal inventories of the aerosol species is as low as 5% for NH4 + and as high as 23% for MSA. The seasonal inventory estimations do not take into consideration the spatial variability caused by blowing and drifting snow. Overall, results indicate that snow deposition of chemical species is the dominant flux mechanism during the summer at Summit and that all three deposition processes should be considered when estimating atmospheric concentrations based on ice core chemical signals.
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Helmig, D, J Boulter, D David, J. Birks, N. Cullen, K Steffen, B. J. Johnson and S. J. Oltmans, (2002), Ozone and meteorological Summit, Greenland, boundary-layer conditions at during 3-21 June 2000, Atmospheric Environment, 36, 15-16, 2595-2608,

Abstract

The temporal and spatial distributions of boundary-layer ozone were studied during June 2000 at Summit, Greenland, using surface-level measurements and vertical profiling from a tethered balloon platform. Three weeks of continuous ozone surface data, 133 meteorological vertical profile data and 82 ozone vertical profile data sets were collected from the surface to a maximum altitude of 1400 m above ground. The lower atmosphere at Summit was characterized by the prevalence of strong stable conditions with strong surface temperature inversions. These inversions reversed to neutral to slightly unstable conditions between similar to9.00 and 18.00 h local time with the formation of shallow mixing heights of similar to70-250 m above the surface. The surface ozone mixing ratio ranged from 39 to 68 ppbv and occasionally had rapid changes of up to 20 ppb in 12 h. The diurnal mean ozone mixing ratio showed diurnal trends indicating meteorological and photochemical controls of surface ozone. Vertical profiles were within the range of 37-76 ppb and showed strong stratification in the lower troposphere. A high correlation of high ozone/low water vapor air masses indicated the transport of high tropospheric/low stratospheric air into the lower boundary layer. A similar to0.1-3 ppb decline of the ozone mixing ratio towards the surface was frequently observed within the neutrally stable mixed layer during midday hours. These data suggest that the boundary-layer ozone mixing ratio and ozone depletion and deposition to the snowpack are influenced by photochemical processes and/or transport phenomena that follow diurnal dependencies. With 37 ppb of ozone being the lowest mixing ratio measured in all data no evidence was seen for the occurrence of ozone depletion episodes similar to those that have been reported within the boundary layer at coastal Arctic sites during springtime.
Helmig, D, S. J. Oltmans, D CARLSON, J LAMARQUE, A JONES, C LABUSCHAGNE, K ANLAUF and K HAYDEN, (2007), A review of surface ozone in the polar regions, Atmospheric Environment, 41, 24, 5138-5161, doi:10.1016/j.atmosenv.2006.09.053

Abstract

Surface ozone records from ten polar research stations were investigated for the dependencies of ozone on radiative processes, snow-photochemisty, and. synoptic and stratospheric transport. A total of 146 annual data records for the Arctic sites Barrow, Alaska; Summit, Greenland; Alert, Canada; Zeppelinfjellet, Norway; and the Antarctic stations Halley, McMurdo, Neumayer, Sanae, Syowa, and South Pole were analyzed. Mean ozone at the Northern Hemisphere (NH) stations (excluding Summit) is similar to 5ppbv higher than in Antarctica. Statistical analysis yielded best estimates for the projected year 2005 median annual ozone mixing ratios, which for the Arctic stations were 33.5 ppbv at Alert, 28.6 ppbv at Barrow, 46.3ppbv ppb at Summit and 33.7ppbv at Zeppelinfjellet. For the Antarctic stations the corresponding ozone mixing ratios were 21.6 ppbv at Halley, 27.0 ppbv at McMurdo, 24.9 ppbv at Neumayer, 27.2 ppbv at Sanae, 29.4 ppbv at South Pole, and 25.8 ppbv at Syowa. At both Summit (3212m asl) and South Pole (2830m asl), annual mean ozone is higher than at the lower elevation and coastal stations. A trend analysis revealed that all sites in recent years have experienced low to moderate increases in surface ozone ranging from 0.02 to 0.26 ppbv yr(-1), albeit none of these changes were found to be statistically significant trends. A seasonal trend analysis showed above-average increases in ozone during the spring and early summer periods for both Arctic (Alert, Zeppelinfjellet) and Antarctic (McMurdo, Neumayer, South Pole) sites. In contrast, at Barrow, springtime ozone has been declining. All coastal stations experience springtime episodes with rapid depletion of ozone in the boundary layer, attributable to photochemically catalyzed ozone depletion from halogen chemistry. This effect is most obvious at Barrow, followed by Alert. Springtime depletion episodes are less pronounced at Antarctic stations. At South Pole, during the Antarctic spring and summer, photochemical ozone production yields frequent episodes with enhanced surface ozone. Other Antarctic stations show similar, though less frequent spring and summertime periods with enhanced ozone. The Antarctic data provide evidence that austral spring and summertime ozone production in Antarctica is widespread, respectively, affects all stations at least through transport events. This ozone production contributes to a several ppbv enhancement in the annual mean ozone over the Antarctic plateau; however, it is not the determining process in the Antarctic seasonal ozone cycle. Although Summit and South Pole have many similarities in their environmental conditions, this ozone production does not appear to be of equal importance at Summit. Amplitudes of diurnal, summertime ozone cycles at these polar sites are weaker than at lower latitude locations. Amplitudes of seasonal ozone changes are larger in the Southern Hemisphere (by similar to 5 ppbv), most likely due to less summertime photochemical ozone loss and more transport of ozone-rich air to the Arctic during the NH spring and summer months.
Helmig, D, S. J. Oltmans, T MORSE and J DIBB, (2007), What is causing high ozone at Summit, Greenland?, Atmospheric Environment, 41, 24, 5031-5043, doi:10.1016/j.atmosenv.2006.05.084

Abstract

Causes for the unusually high and seasonally anomalous ozone concentrations at Summit, Greenland were investigated. Surface data from continuous monitoring, ozone sonde data, tethered balloon vertical profiling data, correlation of ozone with the radionuclide tracers Be-7 and Pb-210, and synoptic transport analysis were used to identify processes that contribute to sources and sinks of ozone at Summit. Northern Hemisphere (NH) lower free troposphere ozone mixing ratios in the polar regions are similar to 20 ppbv higher than in Antarctica. Ozone at Summit, which is at 3212m above sea level, reflects its altitude location in the lower free troposphere. Transport events that bring high ozone and dry air, likely from lower stratospheric/higher tropospheric origin, were observed similar to 40% of time during June 2000. Comparison of ozone enhancements with radionuclide tracer records shows a year-round correlation of ozone with the stratospheric tracer Be-7. Summit lacks the episodic, sunrise ozone depletion events, which were found to reduce the annual, median ozone at NH coastal sites by up to similar to 3 ppbv. Synoptic trajectory analyses indicated that, under selected conditions, Summit encounters polluted continental air with increased ozone from central and western Europe. Low ozone surface deposition fluxes over long distances upwind of Summit reduce ozone deposition losses in comparison to other NH sites, particularly during the summer months. Surface-layer photochemical ozone production does not appear to have a noticeable influence on Summit's ozone levels. (C) 2007 Published by Elsevier Ltd.
Helmig, D., F BOCQUET, L COHEN and S. J. Oltmans, (2007), Ozone uptake to the polar snowpack at Summit, Greenland, Atmospheric Environment, 41, 24, 5061-5076, doi:10.1016/j.atmosenv.2006.06.064

Abstract

The uptake of atmospheric ozone to the polar, year-round snowpack on glacial ice was studied at Summit, Greenland during three experiments in 2003, 2004, and 2005. Ozone was measured at up to three depths in the snowpack, on the surface, and above the surface at three heights on a tower along with supporting meteorological parameters. Ozone in interstitial air decreased with depth, albeit ozone gradients showed a high variation depending on environmental conditions of solar radiation and wind speed. Under low irradiance levels, up to 90% of ozone was preserved up to 1 m depth in the snowpack. Ozone depletion rates increased significantly with the seasonal and diurnal cycle of solar irradiance, resulting in only 10% of ozone remaining in the snowpack following solar noon during summertime. Faster snowpack air exchange from wind pumping resulted in smaller above-surface-to-within snowpack ozone gradients. These data indicate that the uptake of ozone to polar snowpack is strongly dependent on solar irradiance and wind pumping. Ozone deposition fluxes to the polar snowpack are consequently expected to follow incoming solar radiation levels and to exhibit diurnal and seasonal cycles. The Summit observations are in stark contrast to recent findings in the seasonal, midlatitude snowpack [Bocquet, F., Helmig, D., Oltmans, S.J., 2007. Ozone in the mid-latitude snowpack at Niwot Ridge, Colorado. Arctic, Antarctic and Alpine Research, in press], where mostly light-independent ozone behavior was observed. These contrasting results imply different ozone chemistry and snowpack–atmosphere gas exchange in the snow-covered polar, glacial conditions compared to the temperate, mid-latitude environment.
Helmig, D., Neff, W., L. D. Cohen, F. Bocquet, Samuel J. Oltmans, Andrey A. Grachev, (2009), Spring and summertime diurnal surface ozone fluxes over the polar snow at Summit, Greenland, Geophysical Research Letters, 36, L08809, 10.1029/2008gl036549

Abstract

Continuous surface-layer ozone flux measurements over the polar, year-round snowpack at Summit, Greenland, resulted in deposition velocities (v(d)) that were smaller than most previous assumptions and model inputs. Substantial seasonal differences were seen in the ozone v(d) behavior. Spring, daytime ozone v(d) values showed low variability and were consistently <= 0.01 cm s(-1). During summer, ozone fluxes displayed distinct diurnal cycles, and evidence for regular occurrences of bi-directional behavior. Summer, daytime v(d) ranged between similar to 0.01 to 0.07 cm s(-1). Maximum summertime downward fluxes (ozone deposition) coincided with the hours of maximum solar radiation, i.e., noon afternoon. During summer nighttime hours upward ozone fluxes were observed. These upward fluxes were interpreted as ozone production in a shallow layer near and above the snow surface with resulting upward ozone fluxes out of the shallow surface layer. Comparisons with published observations from temperate, midlatitude sites suggest different controls and behavior of ozone fluxes, and that ozone fluxes over snow depend on a myriad of parameters, including solar irradiance, snow chemical and physical properties, snowpack depth, and the type of substrate underneath the snow. Citation: Helmig, D., L. D. Cohen, F. Bocquet, S. Oltmans, A. Grachev, and W. Neff (2009), Spring and summertime diurnal surface ozone fluxes over the polar snow at Summit, Greenland, Geophys. Res. Lett., 36, L08809, doi:10.1029/2008GL036549.
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Kahl, J. D. W., D. A. Martinez, H. Kuhns, C. I. Davidson, J.-L. Jaffrezo and J. M. Harris, (1997), Air mass trajectories to Summit, Greenland: A 44-year climatology and some episodic events, Journal of Geophysical Research-Oceans, 102, C12, 26861-26875, 97JC0029

Abstract

The seasonal variation in atmospheric transport patterns to Summit, Greenland, is examined using a 44-year record of daily, 10-day, isobaric back trajectories at the 500-hPa level. Over 24,000 modeled trajectories are aggregated into distinct patterns using cluster analysis. Ten-day trajectories reaching Summit are longest during winter, with 67% extending upwind (westward) as far back as Asia or Europe. Trajectories are shortest during summer, with 46% having 10-day origins over North America. During all seasons a small percentage (3–7%) of trajectories originate in west Asia/Europe and follow a meridional path over the Arctic Ocean before approaching Summit from the northwest. Trajectories at the 700-hPa level tend to be shorter than at 500 hPa, with many of the 700-hPa trajectories from North America tracking over the North Atlantic and approaching Summit from the south. The long-range transport climatology for Summit is similar to a year-round climatology prepared for Dye 3, located 900 km to the south [Davidson et al., 1993b]. An analysis of several aerosol species measured at Summit during summer 1994 reveals examples of the usefulness and also the limitations of using long-range air trajectories to interpret chemical data.
Kramer, L. J., D. Helmig, J. F. Burkhart, A. Stohl, S. Oltmans and R. E. Honrath, (2015), Seasonal variability of atmospheric nitrogen oxides and non-methane hydrocarbons at the GEOSummit station, Greenland, Atmospheric Chemistry and Physics, 15, 12, 10.5194/acp-15-6827-2015

Abstract

Measurements of atmospheric nitrogen oxides NOx (NOx = NO + NO2), peroxyacetyl nitrate (PAN), NOy, and non-methane hydrocarbons (NMHC) were taken at the Greenland Environmental Observatory at Summit (GEOSummit) station, Greenland (72.34° N, 38.29° W; 3212 m a.s.l.), from July 2008 to July 2010. The data set represents the first year-round concurrent record of these compounds sampled at a high latitude Arctic site. Here, the study focused on the seasonal variability of these important ozone (O3) precursors in the Arctic troposphere and the impact from transported anthropogenic and biomass burning emissions. Our analysis shows that PAN is the dominant NOy species in all seasons at Summit, varying from 42 to 76 %; however, we find that odd NOy species (odd NOy = NOy − PAN − NOx) contribute a large amount to the total NOy speciation. We hypothesize that the source of this odd NOy is most likely alkyl nitrates and nitric acid (HNO3) from transported pollution, and photochemically produced species such as nitrous acid (HONO).

FLEXPART retroplume analyses and black carbon (BC) tracers for anthropogenic and biomass burning (BB) emissions were used to identify periods when the site was impacted by polluted air masses. Europe contributed the largest source of anthropogenic emissions during the winter months (November–March) with 56 % of the total anthropogenic BC tracer originating from Europe in 2008–2009 and 69 % in 2009–2010. The polluted plumes resulted in mean enhancements above background levels up to 334, 295, 88, and 1119 pmol mol−1 for NOy, PAN, NOx, and ethane, respectively, over the two winters. Enhancements in O3 precursors during the second winter were typically higher, which may be attributed to the increase in European polluted air masses transported to Summit in 2009–2010 compared to 2008–2009. O3 levels were highly variable within the sampled anthropogenic plumes with mean ΔO3 levels ranging from −6.7 to 7.6 nmol mol−1 during the winter periods.

North America was the primary source of biomass burning emissions during the summer; however, only 13 BB events were observed as the number of air masses transported to Summit, with significant BB emissions, was low in general during the measurement period. The BB plumes were typically very aged, with median transport times to the site from the source region of 14 days. The analyses of O3 and precursor levels during the BB events indicate that some of the plumes sampled impacted the atmospheric chemistry at Summit, with enhancements observed in all measured species.
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Miller, J.E., J.D.W. Kahl, F. Heller and J. M. Harris, (2002), A three-dimensional residence-time analysis of potential summertime atmospheric transport to Summit, Greenland, Annals of Glaciology, 35, 1, 403-408, doi:10.3189/172756402781816663

Abstract

The interannual variations in atmospheric transport patterns to Summit, Greenland, are studied using twice-daily, three-dimensional, 10day backward trajectory data corresponding to the summers (1June-31August) of 1989-98.While previous trajectory climatology studies have been prepared for Summit, the present work considers both the horizontal and vertical components of transport. A three-dimensional residence-time methodology is employed to account for both horizontal and vertical components of transport. The vertical transport component is quantified by passing all trajectories through a three-dimensional grid and tracking the time spent (i.e. the residence time) in each gridcell. This method also allows inspection of trajectory altitude distributions corresponding to transport from upwind regions of interest.The three-dimensional residence-time methodology is shown to be a valuable tool for diagnosing the details of long-range atmospheric transport to remote locations. For Summit, we find that the frequent transport from North America tends to occur at low altitudes, whereas transport from Europe is highly variable. Mean summertime flow patterns are described, as are anomalous patterns during 1990, 1996 and 1998.
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Neely, Ryan R., Matthew Hayman, Robert Stillwell, Jeffrey P. Thayer, R. Michael Hardesty, Michael O'Neill, Matthew D. Shupe and Catherine Alvarez, (2013), Polarization Lidar at Summit, Greenland, for the Detection of Cloud Phase and Particle Orientation, Journal of Atmospheric and Oceanic Technology, 30, 8, 1635-1655, 10.1175/JTECH-D-12-00101.1

Abstract

Accurate measurements of cloud properties are necessary to document the full range of cloud conditions and characteristics. The Cloud, Aerosol Polarization and Backscatter Lidar (CAPABL) has been developed to address this need by measuring depolarization, particle orientation, and the backscatter of clouds and aerosols. The lidar is located at Summit, Greenland (72.6°N, 38.5°W; 3200 m MSL), as part of the Integrated Characterization of Energy, Clouds, Atmospheric State, and Precipitation at Summit Project and NOAA's Earth System Research Laboratory's Global Monitoring Division's lidar network. Here, the instrument is described with particular emphasis placed upon the implementation of new polarization methods developed to measure particle orientation and improve the overall accuracy of lidar depolarization measurements. Initial results from the lidar are also shown to demonstrate the ability of the lidar to observe cloud properties.

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Petrenko, V. V., P. Martinerie, P. Novelli, D. M. Etheridge, I. Levin, Z. Wang, T. Blunier, J. Chappellaz, J. Kaiser, P. Lang, L. P. Steele, S. Hammer, J. Mak, R. L. Langenfelds, J. Schwander, J. P. Severinghaus, E. Witrant, G. Petron, M. O. Battle, G. Forster, W. T. Sturges, J.-F. Lamarque, K. Steffen and J. W. C. White, (2013), A 60 yr record of atmospheric carbon monoxide reconstructed from Greenland firn air, Atmospheric Chemistry and Physics, 13, 15, 7567-7585, 10.5194/acp-13-7567-2013

Abstract

We present the first reconstruction of the Northern Hemisphere (NH) high latitude atmospheric carbon monoxide (CO) mole fraction from Greenland firn air. Firn air samples were collected at three deep ice core sites in Greenland (NGRIP in 2001, Summit in 2006 and NEEM in 2008). CO records from the three sites agree well with each other as well as with recent atmospheric measurements, indicating that CO is well preserved in the firn at these sites. CO atmospheric history was reconstructed back to the year 1950 from the measurements using a combination of two forward models of gas transport in firn and an inverse model. The reconstructed history suggests that Arctic CO in 1950 was 140–150 nmol mol−1, which is higher than today's values. CO mole fractions rose by 10–15 nmol mol−1 from 1950 to the 1970s and peaked in the 1970s or early 1980s, followed by a ≈ 30 nmol mol−1 decline to today's levels. We compare the CO history with the atmospheric histories of methane, light hydrocarbons, molecular hydrogen, CO stable isotopes and hydroxyl radicals (OH), as well as with published CO emission inventories and results of a historical run from a chemistry-transport model. We find that the reconstructed Greenland CO history cannot be reconciled with available emission inventories unless unrealistically large changes in OH are assumed. We argue that the available CO emission inventories strongly underestimate historical NH emissions, and fail to capture the emission decline starting in the late 1970s, which was most likely due to reduced emissions from road transportation in North America and Europe.

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Schmeisser, Lauren, John Backman, John A. Ogren, Elisabeth Andrews, Eija Asmi, Sandra Starkweather, Taneil Uttal, Markus Fiebig, Sangeeta Sharma, Kostas Eleftheriadis, Stergios Vratolis, Michael Bergin, Peter Tunved and Anne Jefferson, (2018), Seasonality of aerosol optical properties in the Arctic, Atmospheric Chemistry and Physics, 18, 16, 11599-11622, 10.5194/acp-18-11599-2018

Abstract

Abstract. Given the sensitivity of the Arctic climate to short-lived climate forcers, long-term in situ surface measurements of aerosol parameters are useful in gaining insight into the magnitude and variability of these climate forcings. Seasonality of aerosol optical properties – including the aerosol light-scattering coefficient, absorption coefficient, single-scattering albedo, scattering Ångström exponent, and asymmetry parameter – are presented for six monitoring sites throughout the Arctic: Alert, Canada; Barrow, USA; Pallas, Finland; Summit, Greenland; Tiksi, Russia; and Zeppelin Mountain, Ny-Ålesund, Svalbard, Norway. Results show annual variability in all parameters, though the seasonality of each aerosol optical property varies from site to site. There is a large diversity in magnitude and variability of scattering coefficient at all sites, reflecting differences in aerosol source, transport, and removal at different locations throughout the Arctic. Of the Arctic sites, the highest annual mean scattering coefficient is measured at Tiksi (12.47Mm−1), and the lowest annual mean scattering coefficient is measured at Summit (1.74Mm−1). At most sites, aerosol absorption peaks in the winter and spring, and has a minimum throughout the Arctic in the summer, indicative of the Arctic haze phenomenon; however, nuanced variations in seasonalities suggest that this phenomenon is not identically observed in all regions of the Arctic. The highest annual mean absorption coefficient is measured at Pallas (0.48Mm−1), and Summit has the lowest annual mean absorption coefficient (0.12Mm−1). At the Arctic monitoring stations analyzed here, mean annual single-scattering albedo ranges from 0.909 (at Pallas) to 0.960 (at Barrow), the mean annual scattering Ångström exponent ranges from 1.04 (at Barrow) to 1.80 (at Summit), and the mean asymmetry parameter ranges from 0.57 (at Alert) to 0.75 (at Summit). Systematic variability of aerosol optical properties in the Arctic supports the notion that the sites presented here measure a variety of aerosol populations, which also experience different removal mechanisms. A robust conclusion from the seasonal cycles presented is that the Arctic cannot be treated as one common and uniform environment but rather is a region with ample spatiotemporal variability in aerosols. This notion is important in considering the design or aerosol monitoring networks in the region and is important for informing climate models to better represent short-lived aerosol climate forcers in order to yield more accurate climate predictions for the Arctic.

Shupe, Matthew D., David D. Turner, Von P. Walden, Ralf Bennartz, Maria P. Cadeddu, Benjamin B. Castellani, Christopher J. Cox, David R. Hudak, Mark S. Kulie, Nathaniel B. Miller, Ryan R. Neely and W. Neff, (2012), High and Dry: New Observations of Tropospheric and Cloud Properties above the Greenland Ice Sheet, Bulletin of the American Meteorological Society, 10.1175/BAMS-D-11-00249.1

Abstract

Cloud and atmospheric properties strongly influence the mass and energy budgets of the Greenland Ice Sheet (GIS). To address critical gaps in the understanding of these systems, a new suite of cloud- and atmosphere-observing instruments has been installed on the central GIS as part of the Integrated Characterization of Energy, Clouds, Atmospheric State, and Precipitation at Summit (ICECAPS) project. During the first 20 months in operation, this complementary suite of active and passive ground-based sensors and radiosondes has provided new and unique perspectives on important cloud–atmosphere properties.

High atop the GIS, the atmosphere is extremely dry and cold with strong near-surface static stability predominating throughout the year, particularly in winter. This low-level thermodynamic structure, coupled with frequent moisture inversions, conveys the importance of advection for local cloud and precipitation formation. Cloud liquid water is observed in all months of the year, even the particularly cold and dry winter, while annual cycle observations indicate that the largest atmospheric moisture amounts, cloud water contents, and snowfall occur in summer and under southwesterly flow. Many of the basic structural properties of clouds observed at Summit, Greenland, particularly for low-level stratiform clouds, are similar to their counterparts in other Arctic regions.

The ICECAPS observations and accompanying analyses will be used to improve the understanding of key cloud–atmosphere processes and the manner in which they interact with the GIS. Furthermore, they will facilitate model evaluation and development in this data-sparse but environmentally unique region.

Stohl, A., E. Andrews, J. F. Burkhart, C. Forster, A. Herber, S. W. Hoch, D. Kowal, C. Lunder, T. Mefford, J. A. Ogren, S. Sharma, N. Spichtinger, K. Stebel, R. S. Stone, J. Strom, K. Torseth, C. Wehrli and K. E. Yttri, (2006), Pan-Arctic enhancements of light absorbing aerosol concentrations due to North American boreal forest fires during summer 2004, Journal of Geophysical Research-Atmospheres, 111, D22, doi:10.1029/2006JD007216

Abstract

During summer of 2004, about 2.7 million hectare of boreal forest burned in Alaska, the largest annual area burned on record, and another 3.1 million hectare burned in Canada. This study explores the impact of emissions from these fires on light absorbing aerosol concentration levels, aerosol optical depths (AOD), and albedo at the Arctic stations Barrow (Alaska), Alert (Canada), Summit (Greenland), and Zeppelin/Ny Alesund on Spitsbergen (Norway). The Lagrangian particle dispersion model FLEXPART was run backward from these sites to identify periods that were influenced by forest fire pollution plumes. It is shown that the fires led to enhanced values of particle light absorption coefficients (sigma(ap)) at all of these sites. Barrow, about 1000 km away from the fires, was affected by several fire pollution plumes, one leading to spectacularly high 3-hour mean sigma(ap) values of up to 32 Mm(-1), more than the highest values measured in Arctic Haze. AOD measurements for a wavelength of 500 nm saturated but were estimated at above 4-5 units, unprecedented in the station records. Fire plumes were transported through the atmospheric column over Summit continuously for 2 months, during which all measured AOD values were enhanced, with maxima up to 0.4-0.5 units. Equivalent black carbon concentrations at the surface at Summit were up to 600 ng m(-3) during two major episodes, and Alert saw at least one event with enhanced sigma(ap) values. FLEXPART results show that Zeppelin was located in a relatively unaffected part of the Arctic. Nevertheless, there was a 4-day period with daily mean sigma(ap) > 0.3 Mm(-1), the strongest episode of the summer half year, and enhanced AOD values. Elevated concentrations of the highly source-specific compound levoglucosan positively confirmed that biomass burning was the source of the aerosols at Zeppelin. In summary, this paper shows that boreal forest fires can lead to elevated concentrations of light absorbing aerosols throughout the entire Arctic. Enhanced AOD values suggest a substantial impact of these plumes on radiation transmission in the Arctic atmosphere. During the passage of the largest fire plume, a pronounced drop of the albedo of the snow was observed at Summit. We suggest that this is due to the deposition of light absorbing particles on the snow, with further potentially important consequences for the Arctic radiation budget.
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Yang, Xin, Anne-M Blechschmidt, Kristof Bognar, Audra McClure–Begley, Sara Morris, Irina Petropavlovskikh, Andreas Richter, Henrik Skov, Kimberly Strong, David Tarasick, Taneil Uttal, Mika Vestenius and Xiaoyi Zhao, (2020), Pan-Arctic surface ozone: modelling vs measurements,

Abstract

Abstract. Within the framework of the International Arctic Systems for Observing the Atmosphere (IASOA), we report a modelling-based study on surface ozone across the Arctic. We use surface ozone from six sites: Summit (Greenland), Pallas (Finland), Barrow (USA), Alert (Canada), Tiksi (Russia), and Villum Research Station (VRS) at Station Nord (North Greenland, Danish Realm), and ozonesonde data from three Canadian sites: Resolute, Eureka, and Alert. Two global chemistry models: a global chemistry transport model (p-TOMCAT) and a global chemistry climate model (UKCA), are used for model-data comparisons. Remotely sensed data of BrO from the GOME-2 satellite instrument and ground-based Multi-axis Differential Optical Absorption Spectroscopy (MAX-DOAS) at Eureka, Canada are used for model validation.

The observed climatology data show that spring surface ozone at coastal sites is heavily depleted, making ozone seasonality at Arctic coastal sites distinctly different from that at inland sites. Model simulations show that surface ozone can be greatly reduced by bromine chemistry. In April, bromine chemistry can cause a net ozone loss (monthly mean) of 10–20 ppbv, with almost half attributable to open-ocean-sourced bromine and the rest to sea-ice-sourced bromine. However, the open-ocean-sourced bromine, via sea spray bromide depletion, cannot by itself produce ozone depletion events (ODEs) (defined as ozone volume mixing ratios VMRs < 10 ppbv). In contrast, sea-ice-sourced bromine, via sea salt aerosol (SSA) production from blowing snow, can produce ODEs even without bromine from sea spray, highlighting the importance of sea ice surface in polar boundary layer chemistry.

Model bromine is sensitive to model configuration, e.g., under the same bromine loading, the total inorganic bromine (BrY) in the Arctic spring boundary layer in the p-TOMCAT base run (i.e., with all bromine emissions) can be 2 times larger than that in the UKCA base run. Despite the model differences, both model base runs can successfully reproduce large bromine explosion events (BEEs) in polar spring. Model-integrated tropospheric column BrO generally matches GOME-2 tropospheric columns within ~50 % (in the UKCA base run) and factors of 2–3 (in the p-TOMCAT base run). The success of the models in reproducing both ODEs and BEEs in the Arctic indicates that the relevant parameterizations implemented in the models work reasonably well, which supports the proposed mechanism of SSA and bromine production from blowing snow on sea ice. Given that sea ice is a large source of SSA and halogens, changes in sea ice type and extent in a warming climate will influence Arctic boundary layer chemistry, including the oxidation of atmospheric elemental mercury.