Vivier, F, J Hutchings, Y Kawaguchi, T Kikuchi, J Morison, A Lourenço, T Noguchi. (2016). Sea-ice melt onset associated with lead opening during the spring/summer transition near the North Pole . J. Geophys. Res., 121(4), 2499–2522.
Abstract: In the central Arctic Ocean, autonomous observations of the ocean mixed layer and ice documented the transition from cold spring to early summer in 2011. Ice-motion measurements using GPS drifters captured three events of lead opening and ice ridge formation in May and June. Satellite sea ice concentration observations suggest that locally observed lead openings were part of a larger-scale pattern. We clarify how these ice deformation events are linked with the onset of basal sea ice melt, which preceded surface melt by 20 days. Observed basal melt and ocean warming are consistent with the available input of solar radiation into leads, once the advent of mild atmospheric conditions prevents lead refreezing. We use a one-dimensional numerical simulation incorporating a Local Turbulence Closure scheme to investigate the mechanisms controlling basal melt and upper ocean warming. According to the simulation, a combination of rapid ice motion and increased solar energy input at leads promotes basal ice melt, through enhanced mixing in the upper mixed layer, while slow ice motion during a large lead opening in mid-June produced a thin, low-density surface layer. This enhanced stratification near the surface facilitates storage of solar radiation within the thin layer, instead of exchange with deeper layers, leading to further basal ice melt preceding the upper surface melt.
Programme: 1015
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Serdal Ayhan, Mario Pauli, Steffen Scherr, Benjamin Göttel, Akanksha Bhutani, Sven Thomas, Timo Jaeschke, Jean-Michel Panel, Frédéric Vivier, Laurence Eymard, Alain Weill, Nils Pohl, Thomas Zwick. (2017). Millimeter-Wave Radar Sensor for Snow Height Measurements (Vol. 55).
Abstract: A small and lightweight frequency-modulated continuous-wave (FMCW) radar system is used for the determination of snow height by measuring the distance to the snow surface from a platform. The measurements have been performed at the Centre des Études de la Neige (Col de Porte), which is located near Grenoble in the French Alps. It is shown that the FMCW radar at millimeter-wave frequencies is an extremely promising approach for distance measurements to snow surfaces, e.g., in the mountains or in an Arctic environment. The characteristics of the radar sensor are described in detail. The relevant accuracy to measure the distance to a snow layer is shown at different heights and over an extended time duration. A dedicated laser snow telemeter is used as reference. In addition, the reflection from different types of snow is shown.
Keywords: Frequency-modulated continuous-wave (FMCW) radar high accuracy Laser radar Measurement by laser beam millimeter wave Millimeter wave radar Radar measurements range detection Snow snow height snow thickness Temperature measurement
Programme: 1015
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C. Rousset, M. Vancoppenolle, G. Madec, T. Fichefet, S. Flavoni, A. Barthélemy, R. Benshila, J. Chanut, C. Levy, S. Masson, F. Vivier. (2015). The Louvain-La-Neuve sea ice model LIM3.6: global and regional capabilities (Vol. 8). Bachelor's thesis, , .
Abstract: Abstract. The New 3.6 Version Of The Louvain-la-neuve Sea Ice Model (Lim) Is Presented, As Integrated In The Most Recent Stable Release Of Nucleus For European Modelling Of The Ocean (Nemo) (3.6). The Release Will Be Used For The Next Climate Model Inter-comparison Project (Cmip6). Developments Focussed Around Three Axes: Improvements Of Robustness, Versatility And Sophistication Of The Code, Which Involved Numerous Changes. Robustness Was Improved By Enforcing Exact Conservation Through The Inspection Of The Different Processes Driving The Air–ice–ocean Exchanges Of Heat, Mass And Salt. Versatility Was Enhanced By Implementing Lateral Boundary Conditions For Sea Ice And More Flexible Ice Thickness Categories. The Latter Includes A More Practical Computation Of Category Boundaries, Parameterizations To Use Lim3.6 With A Single Ice Category And A Flux Redistributor For Coupling With Atmospheric Models That Cannot Handle Multiple Sub-grid Fluxes. Sophistication Was Upgraded By Including The Effect Of Ice And Snow Weight On The Sea Surface. We Illustrate Some Of The New Capabilities Of The Code In Two Standard Simulations. One Is An Orca2-lim3 Global Simulation At A Nominal 2° Resolution, Forced By Reference Atmospheric Climatologies. The Other One Is A Regional Simulation At 2 Km Resolution Around The Svalbard Archipelago In The Arctic Ocean, With Open Boundaries And Tides. We Show That The Lim3.6 Forms A Solid And Flexible Base For Future Scientific Studies And Model Developments.
Programme: 1015,1244
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Douglas Thomas A, Domine Florent, Barret Manuel, Anastasio Cort, Beine Harry J, Bottenheim Jan, Grannas Amanda, Houdier Stephan, Netcheva Stoyka, Rowland Glenn, Staebler Ralf, Steffen Alexandra,. (2012). Frost flowers growing in the Arctic ocean-atmosphere-sea ice-snow interface: 1. Chemical composition. J. Geophys. Res., 117, D00R09 ST -.
Abstract: Frost flowers, intricate featherlike crystals that grow on refreezing sea ice leads, have been implicated in lower atmospheric chemical reactions. Few studies have presented chemical composition information for frost flowers over time and many of the chemical species commonly associated with Polar tropospheric reactions have never been reported for frost flowers. We undertook this study on the sea ice north of Barrow, Alaska to quantify the major ion, stable oxygen and hydrogen isotope, alkalinity, light absorbance by soluble species, organochlorine, and aldehyde composition of seawater, brine, and frost flowers. For many of these chemical species we present the first measurements from brine or frost flowers. Results show that major ion and alkalinity concentrations, stable isotope values, and major chromophore (NO3- and H2O2) concentrations are controlled by fractionation from seawater and brine. The presence of these chemical species in present and future sea ice scenarios is somewhat predictable. However, aldehydes, organochlorine compounds, light absorbing species, and mercury (part 2 of this research and Sherman et al. (2012)) are deposited to frost flowers through less predictable processes that probably involve the atmosphere as a source. The present and future concentrations of these constituents in frost flowers may not be easily incorporated into future sea ice or lower atmospheric chemistry scenarios. Thinning of Arctic sea ice will likely present more open sea ice leads where young ice, brine, and frost flowers form. How these changing ice conditions will affect the interactions between ice, brine, frost flowers and the lower atmosphere is unknown.
Keywords: frost flowers polar atmospheric chemistry sea ice 0738 Cryosphere: Ice (1863) 0750 Cryosphere: Sea ice (4540) 0793 Cryosphere: Biogeochemistry (0412, 0414, 1615, 4805, 4912) 1022 Geochemistry: Composition of the hydrosphere 1050 Geochemistry: Marine geochemistry (4835, 4845, 4850),
Programme: 1017
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Domine Florent, Gallet Jean-Charles, Barret Manuel, Houdier Stphan, Voisin Didier, Douglas Thomas A, Blum Joel D, Beine Harry J, Anastasio Cort, Bron Franois-Marie, . (2011). The specific surface area and chemical composition of diamond dust near Barrow, Alaska
. J. Geophys. Res., 116, D00R06–.
Abstract: Diamond dust (DD) refers to tiny ice crystals that form frequently in the Polar troposphere under clear sky conditions. They provide surfaces for chemical reactions and scatter light. We have measured the specific surface area (SSA) of DD at Barrow in March–April 2009. We have also measured its chemical composition in mineral and organic ions, dissolved organic carbon (DOC), aldehydes, H2O2, and the absorption spectra of water-soluble chromophores. Mercury concentrations were also measured in spring 2006, when conditions were similar. The SSA of DD ranges from 79.9 to 223 m2 kg-1. The calculated ice surface area in the atmosphere reaches 11000 (70%) μm2 cm-3, much higher than the aerosol surface area. However, the impact of DD on the downwelling and upwelling light fluxes in the UV and visible is negligible. The composition of DD is markedly different from that of snow on the surface. Its concentrations in mineral ions are much lower, and its overall composition is acidic. Its concentrations in aldehydes, DOC, H2O2 and mercury are much higher than in surface snows. Our interpretation is that DOC from the oceanic surface microlayer, coming from open leads in the ice off of Barrow, is taken up by DD. Active chemistry in the atmosphere takes place on DD crystal surfaces, explaining its high concentrations in aldehydes and mercury. After deposition, active photochemistry modifies DD composition, as seen from the modifications in its absorption spectra and aldehyde and H2O2 content. This probably leads to the emissions of reactive species to the atmosphere.
Keywords: absorption spectra, aldehydes, dissolved organic carbon, ionic composition, mercury, specific surface area, 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801, 4906), 0317 Atmospheric Composition and Structure: Chemical kinetic and photochemical properties, 0330 Atmospheric Composition and Structure: Geochemical cycles (1030), 0365 Atmospheric Composition and Structure: Troposphere: composition and chemistry, 0736 Cryosphere: Snow (1827, 1863),
Programme: 1017
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France J L, King M D, Lee-Taylor J, Beine H J, Ianniello A, Domine F, MacArthur A,. (2011). Calculations of in-snow NO2 and OH radical photochemical production and photolysis rates: A field and radiative-transfer study of the optical properties of Arctic (Ny-Ålesund, Svalbard) snow. J. Geophys. Res., 116, F04013 ST -.
Abstract: Depth-integrated production rates of OH radicals and NO2 molecules from snowpacks in Ny-Ålesund, Svalbard, are calculated from fieldwork investigating the light penetration depth (e-folding depth) and nadir reflectivity of snowpacks during the unusually warm spring of 2006. Light penetration depths of 8.1, 11.3, 5.1, and 8.2 cm were measured for fresh, old, marine-influenced, and glacial snowpacks, respectively (wavelength 400 nm). Radiative-transfer calculations of the light penetration depths with reflectivity measurements produced scattering cross sections of 5.3, 9.5, 20, and 25.5 m2 kg-1 and absorption cross sections of 7.7, 1.4, 3.4, and 0.5 cm2 kg-1 for the fresh, old, marine-influenced, and glacial snowpacks, respectively (wavelength 400 nm). Photolysis rate coefficients, J, are presented as a function of snow depth and solar zenith angle for the four snowpacks for the photolysis of H2O2 and NO3-. Depth-integrated production rates of hydroxyl radicals are 1270, 2130, 950, and 1850 nmol m-2 h-1 (solar zenith angle of 60°) for fresh, old, marine-influenced, and glacial snowpacks, respectively. Depth-integrated production rates of NO2 are 32, 56, 11, and 22 nmol m-2 h-1 (solar zenith angle of 60°) for the fresh, old, marine-influenced, and glacial snowpacks, respectively. The uncertainty of repeated light penetration depth measurement was determined to be ~20%, which propagates into a 20% error in depth-integrated production rates. A very simple steady state hydroxyl radical calculation demonstrates that a pseudo first-order loss rate of OH radicals of ~102–104 s-1 is required in snowpack. The snowpacks around Ny-Ålesund are thick enough to be considered optically infinite.
Keywords: Arctic fluxes hydroxyl radical nitrate snowpack 0736 Cryosphere: Snow (1827, 1863) 0798 Cryosphere: Modeling (1952, 4316),
Programme: 1017
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Barret Manuel, Domine Florent, Houdier Stephan, Gallet Jean-Charles, Weibring Petter, Walega James, Fried Alan, Richter Dirk, . (2011). Formaldehyde in the Alaskan Arctic snowpack: Partitioning and physical processes involved in air-snow exchanges
. J. Geophys. Res., 116, D00R03–.
Abstract: The snowpack is a photochemically active medium which produces numerous key reactive species involved in the atmospheric chemistry of polar regions. Formaldehyde (HCHO) is one such reactive species produced in the snow, and which can be released to the atmospheric boundary layer. Based on atmospheric and snow measurements, this study investigates the physical processes involved in the HCHO air-snow exchanges observed during the OASIS 2009 field campaign at Barrow, Alaska. HCHO concentration changes in a fresh diamond dust layer are quantitatively explained by the equilibration of a solid solution of HCHO in ice, through solid-state diffusion of HCHO within snow crystals. Because diffusion of HCHO in ice is slow, the size of snow crystals is a major variable in the kinetics of exchange and the knowledge of the snow specific surface area is therefore crucial. Air-snow exchanges of HCHO can thus be explained without having to consider processes taking place in the quasi-liquid layer present at the surface of ice crystals. A flux of HCHO to the atmosphere was observed simultaneously with an increase of HCHO concentration in snow, indicating photochemical production in surface snow. This study also suggests that the difference in bromine chemistry between Alert (Canadian Arctic) and Barrow leads to different snow composition and post-deposition evolutions. The highly active bromine chemistry at Barrow probably leads to low HCHO concentrations at the altitude where diamond dust formed. Precipitated diamond dust was subsequently undersaturated with respect to thermodynamic equilibrium, which contrasts to what was observed elsewhere in previous studies.
Keywords: adsorption, carbonyls, diffusion, halogen, solid-solution, 0322 Atmospheric Composition and Structure: Constituent sources and sinks, 0365 Atmospheric Composition and Structure: Troposphere: composition and chemistry, 0736 Cryosphere: Snow (1827, 1863), 3307 Atmospheric Processes: Boundary layer processes, 9315 Geographic Location: Arctic region (0718, 4207),
Programme: 1017
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Voisin Didier, Jaffrezo Jean-Luc, Houdier Stphan, Barret Manuel, Cozic Julie, King Martin D, France James L, Reay Holly J, Grannas Amanda, Kos Gregor, Ariya Parisa A, Beine Harry J, Domine Florent, . (2012). Carbonaceous species and humic like substances (HULIS) in Arctic snowpack during OASIS field campaign in Barrow
. J. Geophys. Res., 117, D00R19–.
Abstract: Snowpacks contain many carbonaceous species that can potentially impact on snow albedo and arctic atmospheric chemistry. During the OASIS field campaign, in March and April 2009, Elemental Carbon (EC), Water insoluble Organic Carbon (WinOC) and Dissolved Organic Carbon (DOC) were investigated in various types of snow: precipitating snows, remobilized snows, wind slabs and depth hoars. EC was found to represent less than 5% of the Total Carbon Content (TCC = EC + WinOC + DOC), whereas WinOC was found to represent an unusual 28 to 42% of TCC. Snow type was used to infer physical processes influencing the evolution of different fractions of DOC. DOC is highest in soil influenced indurated depth hoar layers due to specific wind related formation mechanisms in the early season. Apart from this specific snow type, DOC is found to decrease from precipitating snow to remobilized snow to regular depth hoar. This decrease is interpreted as due to cleaving photochemistry and physical equilibration of the most volatile fraction of DOC. Depending on the relative proportions of diamond dust and fresh snow in the deposition of the seasonal snowpack, we estimate that 31 to 76% of DOC deposited to the snowpack is reemitted back to the boundary layer. Under the assumption that this reemission is purely photochemical, we estimate an average flux of VOC out of the snowpack of 20 to 170 μgC m-2 h-1. Humic like substances (HULIS), short chain diacids and aldehydes are quantified, and showed to represent altogether a modest (<20%) proportion of DOC, and less than 10% of DOC + WinOC. HULIS optical properties are measured and could be consistent with aged biomass burning or a possible marine source.
Keywords: HULIS, OASIS, carbonaceous species, snow chemistry, snow metamorphism, 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801, 4906), 0706 Cryosphere: Active layer, 0736 Cryosphere: Snow (1827, 1863),
Programme: 1017
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Morin S, Erbland J, Savarino J, Domine F, Bock J, Friess U, Jacobi H-W, Sihler H, Martins J M F, . (2012). An isotopic view on the connection between photolytic emissions of NOx from the Arctic snowpack and its oxidation by reactive halogens
. J. Geophys. Res., 117, D00R08–.
Abstract: We report on dual isotopic analyses (δ15N and Δ17O) of atmospheric nitrate at daily time-resolution during the OASIS intensive field campaign at Barrow, Alaska, in March–April 2009. Such measurements allow for the examination of the coupling between snowpack emissions of nitrogen oxides (NOx = NO + NO2) and their involvement in reactive halogen-mediated chemical reactions in the Arctic atmosphere. The measurements reveal that during the spring, low δ15N values in atmospheric nitrate, indicative of snowpack emissions of NOx, are almost systematically associated with local oxidation of NOx by reactive halogens such as BrO, as indicated by 17O-excess measurements (Δ17O). The high time-resolution data from the intensive field campaign were complemented by weekly aerosol sampling between April 2009 and February 2010. The dual isotopic composition of nitrate (δ15N and Δ17O) obtained throughout this nearly full seasonal cycle is presented and compared to other seasonal-scale measurements carried out in the Arctic and in non-polar locations. In particular, the data allow for the investigation of the seasonal variations of reactive halogen chemistry and photochemical snowpack NOx emissions in the Arctic. In addition to the well characterized peak of snowpack NOx emissions during springtime in the Arctic (April to May), the data reveal that photochemical NOx emissions from the snowpack may also occur in other seasons as long as snow is present and there is sufficient UV radiation reaching the Earth's surface.
Keywords: halogen, isotopes, nitrate, ozone, 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801, 4906), 0365 Atmospheric Composition and Structure: Troposphere: composition and chemistry, 0454 Biogeosciences: Isotopic composition and chemistry (1041, 4870), 0736 Cryosphere: Snow (1827, 1863), 9315 Geographic Location: Arctic region (0718, 4207),
Programme: 1017
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Gouttevin I, Menegoz M, Domin F, Krinner G, Koven C, Ciais P, Tarnocai C, Boike J, . (2012). How the insulating properties of snow affect soil carbon distribution in the continental pan-Arctic area
. J. Geophys. Res., 117(G2), G02020–.
Abstract: We demonstrate the effect of an ecosystem differentiated insulation by snow on the soil thermal regime and on the terrestrial soil carbon distribution in the pan-Arctic area. This is done by means of a sensitivity study performed with the land surface model ORCHIDEE, which furthermore provides a first quantification of this effect. Based on field campaigns reporting higher thermal conductivities and densities for the tundra snowpack than for taiga snow, two distributions of near-equilibrium soil carbon stocks are computed, one relying on uniform snow thermal properties and the other using ecosystem-differentiated snow thermal properties. Those modeled distributions strongly depend on soil temperature through decomposition processes. Considering higher insulation by snow in taiga areas induces warmer soil temperatures by up to 12 K in winter at 50 cm depth. This warmer soil signal persists over summer with a temperature difference of up to 4 K at 50 cm depth, especially in areas exhibiting a thick, enduring snow cover. These thermal changes have implications on the modeled soil carbon stocks, which are reduced by 8% in the pan-Arctic continental area when the vegetation-induced variations of snow thermal properties are accounted for. This is the result of diverse and spatially heterogeneous ecosystem processes: where higher soil temperatures lift nitrogen limitation on plant productivity, tree plant functional types thrive whereas light limitation and enhanced water stress are the new constrains on lower vegetation, resulting in a reduced net productivity at the pan-Arctic scale. Concomitantly, higher soil temperatures yield increased respiration rates (+22% over the study area) and result in reduced permafrost extent and deeper active layers which expose greater volumes of soil to microbial decomposition. The three effects combine to produce lower soil carbon stocks in the pan-Arctic terrestrial area. Our study highlights the role of snow in combination with vegetation in shaping the distribution of soil carbon and permafrost at high latitudes.
Keywords: Arctic, land-surface model, permafrost, snow, snow insulation, soil carbon, 0414 Biogeosciences: Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912), 0475 Biogeosciences: Permafrost, cryosphere, and high-latitude processes (0702, 0716), 1622 Global Change: Earth system modeling (1225, 4316),
Programme: 1017
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