Ardhuin Fabrice, Stutzmann Eleonore, Schimmel Martin, Mangeney Anne, . (2011). Ocean wave sources of seismic noise
. J. Geophys. Res., 116(C9), C09004–.
Abstract: Noise with periods 3 to 10 s, ubiquitous in seismic records, is expected to be mostly generated by pairs of ocean wave trains of opposing propagation directions with half the seismic frequency. Here we present the first comprehensive numerical model of microseismic generation by random ocean waves, including ocean wave reflections. Synthetic and observed seismic spectra are well correlated (r > 0.85). On the basis of the model results, noise generation events can be clustered in three broad classes: wind waves with a broad directional spectrum (class I), sea states with a significant contribution of coastal reflections (class II), and the interaction of two independent wave systems (class III). At seismic stations close to western coasts, noise generated by class II sources generally dominates, but it is intermittently outshined by the intense class III sources, limiting the reliability of seismic data as a proxy for storm climates. The modeled seismic noise critically depends on the damping of seismic waves. At some mid-ocean island stations, low seismic damping is necessary to reproduce the observed high level and smoothness of noise time series that result from a spatial integration of sources over thousands of kilometers. In contrast, some coastal stations are only sensitive to noise within a few hundreds of kilometers. This revelation of noise source patterns worldwide provides a wealth of information for seismic studies, wave climate applications, and new constraints on the possible directional distribution of wave energy.
Keywords: directional wave spectra, ocean waves, seismic noise, wave model, 4259 Ocean acoustics, 4544 Internal and inertial waves, 4560 Surface waves and tides, 7220 Oceanic crust, 7255 Surface waves and free oscillations,
Programme: 133
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Hezel P J, Alexander B, Bitz C M, Steig E J, Holmes C D, Yang X, Sciare J, . (2011). Modeled methanesulfonic acid (MSA) deposition in Antarctica and its relationship to sea ice
. J. Geophys. Res., 116(D23), D23214–.
Abstract: Methanesulfonic acid (MSA) has previously been measured in ice cores in Antarctica as a proxy for sea ice extent and Southern Hemisphere circulation. In a series of chemical transport model (GEOS-Chem) sensitivity experiments, we identify mechanisms that control the MSA concentrations recorded in ice cores. Sea ice is linked to MSA via dimethylsulfide (DMS), which is produced biologically in the surface ocean and known to be particularly concentrated in the sea ice zone. Given existing ocean surface DMS concentration data sets, the model does not demonstrate a strong relationship between sea ice and MSA deposition in Antarctica. The variability of DMS emissions associated with sea ice extent is small (1130%) due to the small interannual variability of sea ice extent. Wind plays a role in the variability in DMS emissions, but its contribution relative to that of sea ice is strongly dependent on the assumed DMS concentrations in the sea ice zone. Atmospheric sulfur emitted as DMS from the sea ice undergoes net transport northward. Our model runs suggest that DMS emissions from the sea ice zone may account for 2662% of MSA deposition at the Antarctic coast and 3695% in inland Antarctica. Though our results are sensitive to model assumptions, it is clear that an improved understanding of both DMS concentrations and emissions from the sea ice zone are required to better assess the impact of sea ice variability on MSA deposition to Antarctica.
Keywords: DMS, MSA, dimethylsulfide, ice core, methanesulfonic acid, sea ice, 0368 Troposphere: constituent transport and chemistry, 0750 Sea ice, 0793 Biogeochemistry, 3344 Paleoclimatology,
Programme: 415
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. (2011). Internal waves and vertical mixing in the Storfjorden Polynya, Svalbard
. Journal of Geophysical Research: Oceans, 116(C12), C12040–.
Keywords: Garret and Munk model, Thorpe scale, barotropic tides, internal waves, latent heat polynya, vertical mixing, 4207 Arctic and Antarctic oceanography, 4544 Internal and inertial waves, 4572 Upper ocean and mixed layer processes,
Programme: 1015
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Hezel P J, Alexander B, Bitz C M, Steig E J, Holmes C D, Yang X, Sciare J, . (2011). Modeled methanesulfonic acid (MSA) deposition in Antarctica and its relationship to sea ice
. Journal of Geophysical Research: Atmospheres, 116(D23), D23214–.
Abstract: Methanesulfonic acid (MSA) has previously been measured in ice cores in Antarctica as a proxy for sea ice extent and Southern Hemisphere circulation. In a series of chemical transport model (GEOS-Chem) sensitivity experiments, we identify mechanisms that control the MSA concentrations recorded in ice cores. Sea ice is linked to MSA via dimethylsulfide (DMS), which is produced biologically in the surface ocean and known to be particularly concentrated in the sea ice zone. Given existing ocean surface DMS concentration data sets, the model does not demonstrate a strong relationship between sea ice and MSA deposition in Antarctica. The variability of DMS emissions associated with sea ice extent is small (1130%) due to the small interannual variability of sea ice extent. Wind plays a role in the variability in DMS emissions, but its contribution relative to that of sea ice is strongly dependent on the assumed DMS concentrations in the sea ice zone. Atmospheric sulfur emitted as DMS from the sea ice undergoes net transport northward. Our model runs suggest that DMS emissions from the sea ice zone may account for 2662% of MSA deposition at the Antarctic coast and 3695% in inland Antarctica. Though our results are sensitive to model assumptions, it is clear that an improved understanding of both DMS concentrations and emissions from the sea ice zone are required to better assess the impact of sea ice variability on MSA deposition to Antarctica.
Keywords: DMS, MSA, dimethylsulfide, ice core, methanesulfonic acid, sea ice, 0368 Troposphere: constituent transport and chemistry, 0750 Sea ice, 0793 Biogeochemistry, 3344 Paleoclimatology,
Programme: 414
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. (2012). Measurements of OH and RO2 radicals at the coastal Antarctic site of Dumont d'Urville (East Antarctica) in summer 20102011
. Journal of Geophysical Research: Atmospheres, 117(D12), D12310–.
Keywords: Antarctic photochemistry, Atmospheric oxidants, Hydroxyl radicals, 0322 Constituent sources and sinks, 0365 Troposphere: composition and chemistry, 0368 Troposphere: constituent transport and chemistry,
Programme: 414
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. (2012). Nitrous acid at Concordia (inland site) and Dumont d'Urville (coastal site), East Antarctica
. Journal of Geophysical Research: Atmospheres, 117(D8), D08303–.
Keywords: East Antarctica, LOPAP, nitrous acid, 0322 Constituent sources and sinks, 0365 Troposphere: composition and chemistry, 0368 Troposphere: constituent transport and chemistry,
Programme: 414;903
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. (2012). Oxidant Production over Antarctic Land and its Export (OPALE) project: An overview of the 20102011 summer campaign
. Journal of Geophysical Research: Atmospheres, 117(D15), D15307–.
Abstract: This paper summarizes the objectives and setting of the OPALE (Oxidant Production over Antarctic Land and its Export) project during summer 2010/2011 at Dumont d'Urville. The primary goal of the campaign is to characterize the oxidizing environment of the atmospheric boundary layer along the coast of East Antarctica. A summary of the relevant field chemical measurements is presented including the carbon monoxide and ammonia records that are used here to identify local influences due to station activities and penguin emissions. An overview of the basic meteorological conditions experienced by the site is presented including the results from the trajectory/dispersion model FLEXPART to highlight which types of air mass were sampled (marine boundary layer versus continental Antarctic air). The results of the FLEXPART analysis demonstrate that high ozone levels and related changes in the OH concentrations are associated with the transport of continental air to DDU. Finally, three companion papers are introduced. A first paper is dedicated to the impact of local penguin emissions on the atmospheric budget of several oxygenated volatile organic compounds. The second paper reports on HONO levels that were measured for the first time in Antarctica by using the long path absorption photometer (LOPAP) technique. Finally, in a third paper, major findings on the HOx levels are detailed, leading to the overall conclusion that the photochemistry at coastal East Antarctica is strongly driven by an efficient HOx chemistry compared to the situation at other coastal Antarctic regions.
Keywords: Antarctic photochemistry, atmospheric oxidants, hydroxyl radicals, nitrous acid, 0315 Biosphere/atmosphere interactions, 0365 Troposphere: composition and chemistry, 0368 Troposphere: constituent transport and chemistry,
Programme: 414
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Ardhuin Fabrice, Balanche Abel, Stutzmann E, Obrebski Mathias, . (2012). From seismic noise to ocean wave parameters: General methods and validation
. Journal of Geophysical Research: Oceans, 117(C5), C05002–.
Keywords: directional spectrum, microseisms, ocean waves, 4546 Nearshore processes, 4560 Surface waves and tides, 4594 Instruments and techniques, 7219 Seismic monitoring and test-ban treaty verification, 7255 Surface waves and free oscillations,
Programme: 133
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Ohtaki Toshiki, Kaneshima Satoshi, Kanjo Kenji, . (2012). Seismic structure near the inner core boundary in the south polar region
. J. Geophys. Res., 117(B3), B03312–.
Keywords: P-wave velocity and attenuation, inner and outer core, south polar region, 1507 Core processes, 7203 Body waves, 7207 Core, 8115 Core processes, 8124 Earth's interior: composition and state,
Programme: 133
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. (2012). A reassessment of the budget of formic and acetic acids in the boundary layer at Dumont d'Urville (coastal Antarctica): The role of penguin emissions on the budget of several oxygenated volatile organic compounds
. Journal of Geophysical Research: Atmospheres, 117(D6), D06308–.
Abstract: Initiated in 1997, the year-round study of formic and acetic acids was maintained until 2011 at the coastal Antarctic site of Dumont d'Urville. The records show that formic and acetic acids are rather abundant in summer with typical mixing ratios of 200 pptv and 700 pptv, respectively. With the aim to constrain their budget, investigations of their potential marine precursors like short-chain alkenes and acetaldehyde were initiated in 2011. Acetic acid levels in December 2010 were four times higher than those observed over summers back to 1997. These unusually high levels were accompanied by unusually high levels of ammonia, and by an enrichment of oxalate in aerosols. These observations suggest that the guano decomposition in the large penguin colonies present at the site was particularly strong under weather conditions encountered in spring 2010 (important snow storms followed by sunny days with mild temperatures). Although being dependent on environmental conditions, this process greatly impacts the local atmospheric budget of acetic acid, acetaldehyde, and acetone during the entire summer season. Present at levels as high as 500 pptv, acetaldehyde may represent the major precursor of acetic acid, alkene-ozone reactions remaining insignificant sources. Far less influenced by penguin emissions, the budget of formic acid remains not fully understood even if alkene-ozone reactions contribute significantly.
Keywords: carboxylic acids, formic and acetic acids, ornithogenic soil emission, oxygenated volatile compounds, 0315 Biosphere/atmosphere interactions, 0330 Geochemical cycles, 0365 Troposphere: composition and chemistry,
Programme: 414;903
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