Simpson, W.R.; Alvarez-Aviles, L.; Douglas, T.A.; Sturm, M.; Domine, F. (2005). Halogens in the coastal snow pack near Barrow, Alaska: Evidence for active bromine air-snow chemistry during springtime. Geophysical research letters, 32.
Abstract: We measured halide concentrations of snow and frost flowers in the vicinity of Barrow, Alaska. We find that the ratio of bromide to sodium in frost flowers is slightly enhanced (?10%) as compared to sea water. In contrast, the ratio of bromide to sodium in some snow samples is more than an order of magnitude enhanced, and in other samples is more than an order of magnitude depleted. We interpret the bromide depleted snow as having been processed by heterogeneous chemistry and providing reactive halogen compounds to the atmosphere. The eventual end product of reactive bromine chemistry is HBr that is then deposited over a wide region, enhancing bromide in inland snow samples. Although frost flowers or open leads are likely to be the original source of halides that become reactive halogen gases, we find that the bromide release often occurs subsequent to production of aerosol from marine sources.
Keywords: 0312 Atmospheric Composition and Structure: Air/sea constituent fluxes; 0330 Atmospheric Composition and Structure: Geochemical cycles; 0365 Atmospheric Composition and Structure: Troposphere: composition and chemistry; 0368 Atmospheric Composition and Structure: Troposphere: constituent transport and chemistry; 1863 Hydrology: Snow and ice
Programme: 437
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. (2004). Can finite-frequency effects be accounted for in ray theory surface wave tomography? Geophysical research letters, 31, L24614.
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Andersen, O.B.; Hinderer, J. (2005). Global inter-annual gravity changes from GRACE: Early results. Geophysical research letters, 32.
Abstract: Fifteen monthly gravity field solutions from the GRACE twin satellites launched more than two years ago have been studied to estimate gravity field changes between 2002 and 2003.The results demonstrate that GRACE is capable of capturing the changes in ground water on inter-annual scales with an accuracy of 0.4 ?Gal corresponding to 9 mm water thickness on spatial scales longer than 1300 km. Four of the most widely used global hydrological models have been investigated for their spatial comparison with GRACE observations of inter-annual gravity field variations due to changes in continental water storage. The Global Land Data Assimilation System model has a spatial correlation coefficient with GRACE observations of 0.65 over the northern hemisphere. This demonstrates that the observed gravity field changes on these scales are largely related to changes in continental water storage.
Keywords: 1217 Geodesy and Gravity: Time variable gravity; 1855 Hydrology: Remote sensing; 1640 Global Change: Remote sensing; 1655 Global Change: Water cycles
Programme: 337
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Marchaudon, A.; Cerisier, J.-C.; Greenwald, R.A.; Sofko, G.J. (2004). Electrodynamics of a flux transfer event: Experimental test of the Southwood model. Geophysical research letters, 31.
Keywords: 2409 Ionosphere: Current systems; 2431 Ionosphere: Ionosphere/magnetosphere interactions; 2463 Ionosphere: Plasma convection; 2784 Magnetospheric Physics: Solar wind/magnetosphere interactions
Programme: 312;911
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Park, Y.-H.; Roquet, F.; Vivier, F. (2004). Quasi-stationary ENSO wave signals versus the Antarctic Circumpolar Wave scenario. Geophysical research letters, 31.
Abstract: Two conflicting views on the causal mechanism of the Antarctic interannual variability often appear in the literature, i.e., whether it is remotely teleconnected to tropical ENSO events or is a self-sustained eastward propagating circumpolar wave generated locally by an ocean-atmosphere coupling mechanism. Using a Fourier decomposition into stationary and propagating components of several oceanic and atmospheric variables, we show that most of the Antarctic interannual variability can be explained by a geographically phase-locked standing wave train linked to tropical ENSO episodes. This ENSO-modulated quasi-stationary variability is not zonally uniform, rather, the strongest ENSO impact is consistently concentrated in the Pacific sector of the Southern Ocean. The eastward propagating wave component is found to be not only minor (25% of variability) but also intermittent in phase, yielding little support for the so-called Antarctic Circumpolar Wave scenario.
Keywords: 4215 Oceanography: General: Climate and interannual variability; 4207 Oceanography: General: Arctic and Antarctic oceanography; 4522 Oceanography: Physical: El Nino
Programme: 335
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Baker, D.F.; Law, R.M.; Gurney, K.R.; Rayner, P.; Peylin, P.; Denning, A.S.; Bousquet, P.; Bruhwiler, L.; Chen, Y.-H.; Ciais, P.; Fung, I.Y.; Heimann, M.; John, J.; Maki, T.; Maksyutov, S.; Masarie, K.; Prather, M.; Pak, B.; Taguchi, S.; Zhu, Z. (2006). Global biogeochemical cycles, 20.
Keywords: atmospheric inversions; CO 2 fluxes; interannual variability; 0368 Atmospheric Composition and Structure: Troposphere: constituent transport and chemistry; 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0428 Biogeosciences: Carbon cycling; 0414 Biogeosciences: Biogeochemical cycles, processes, and modeling; 3260 Mathematical Geophysics: Inverse theory
Programme: 439
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Delmotte, M.; Chappellaz, J.; Brook, E.; Yiou, P.; Barnola, J.M.; Goujon, C.; Raynaud, D.; Lipenkov, V.I. (2004). Atmospheric methane during the last four glacial-interglacial cycles: Rapid changes and their link with Antarctic temperature. J. Geophys. Res., 109.
Keywords: climate; atmospheric methane; ice core; 0325 Atmospheric Composition and Structure: Evolution of the atmosphere; 1610 Global Change: Atmosphere; 1615 Global Change: Biogeochemical processes; 3339 Meteorology and Atmospheric Dynamics: Ocean/atmosphere interactions
Programme: 439;902
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Alexander, B.; Savarino, J.; Kreutz, K.J.; Thiemens, M.H. (2004). Impact of preindustrial biomass-burning emissions on the oxidation pathways of tropospheric sulfur and nitrogen. J. Geophys. Res., 109.
Abstract: Ice core measurements (H2O2 and CH4/HCHO) and modeling studies indicate a change in the oxidation capacity of the atmosphere since the onset of the Industrial Revolution due to increases in fossil fuel burning emissions [e.g., Lelieveld et al., 2002; Hauglustaine and Brasseur, 2001; Wang and Jacob, 1998; Staffelbach et al., 1991]. The mass-independent fractionation (MIF) in the oxygen isotopes of sulfate and nitrate from a Greenland ice core reveal that biomass-burning events in North America just prior to the Industrial Revolution significantly impacted the oxidation pathways of sulfur and nitrogen species deposited in Greenland ice. This finding highlights the importance of biomass-burning emissions for atmospheric chemistry in preindustrial North America and warrants the inclusion of this impact in modeling studies estimating changes in atmospheric oxidant chemistry since the Industrial Revolution, particularly when using paleo-oxidant data as a reference for model evaluation.
Programme: 1011
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Landais, A.; Steffensen, J.P.; Caillon, N.; Jouzel, J.; Masson-Delmotte, V.; Schwander, J. (2004). Evidence for stratigraphic distortion in the Greenland Ice Core Project (GRIP) ice core during Event 5e1 (120 kyr BP) from gas isotopes. J. Geophys. Res., 109.
Abstract: The disturbed stratigraphy of the ice in the lowest 10% of the Greenland GRIP ice core has been previously demonstrated using gas measurements (?18O of O2 and CH4) on a few meters depth scale. However, rapid ice isotopic variations (on the scale of 20 cm) are experienced in the bottom of the GRIP ice core with complex chemical signatures that make them difficult to reconcile with a disturbed stratigraphy of the ice. This is the case for event 5e1, first described as a dramatic cooling 120 kyr BP. We analyzed at a 5 cm resolution the isotopic composition of the air from 2 m of the GRIP bottom ice core covering event 5e1. The ?15N measurements, combined with a basic firn modeling, lead to the solid conclusion that the rapid event 5e1 is not a climatic event. Rapid variations of ?18O of O2 (?18Oatm) are in agreement with a disturbed ice stratigraphy. However, the double peak shape of the ?18Oatm, recalling chemical data at the same depth, requires processes of diffusion after the mixing or even postcoring, placing limits to the interpretation of some classical paleoclimatic proxies in small scale mixed ice (<1 m).
Keywords: 1827 Hydrology: Glaciology; 3344 Meteorology and Atmospheric Dynamics: Paleoclimatology; 3349 Meteorology and Atmospheric Dynamics: Polar meteorology
Programme: 458
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Udisti, R.; Becagli, S.; Castellano, E.; Delmonte, B.; Jouzel, J.; Petit, J.R.; Schwander, J.; Stenni, B.; Wolff, E.W. (2004). Stratigraphic correlations between the European Project for Ice Coring in Antarctica (EPICA) Dome C and Vostok ice cores showing the relative variations of snow accumulation over the past 45 kyr. J. Geophys. Res., 109.
Abstract: High-resolution chemistry analysis and electrical measurements performed on two ice core records (European Project for Ice Coring in Antarctica (EPICA) Dome C and Vostok) spanning the last 45 kyr allow stratigraphic correlations by matching volcanic events. Several common events were identified along the two ice cores on the basis of acidity and sulphate spikes in snow layers. Timescales were matched through comparison with isotope (?D) profiles and using the Antarctic cold reversal (ACR) minimum, a 10Be peak, and a dust spike as temporal checkpoints. Ratios of relative snow accumulation at the two sites during the Holocene, in the glacial-interglacial transition and in the last part of the glacial period, were reconstructed by finding the best fit between Dome C and Vostok depths recording the same events. After accounting for thinning of the layers as they are buried within the glacier, the Dome C-Vostok accumulation ratio, expected to be roughly constant from the conventional accumulation-temperature-isotope approach, is 1.12 for the glacial period but increases to as much as 1.44 for a large part of the Holocene. Glaciological effects, mainly related to the geographic origin of the Vostok ice along the Ridge B-Vostok axis, can account for only a minor fraction of this change. Instead, we argue that accumulation variability between the cores stems from differential changes in atmospheric circulation during these respective climatic periods at the two sites. Regional changes in atmospheric circulation are proposed with a negative anomaly in Dome C, a positive accumulation anomaly in Vostok, or a combination of both during glacial climate. Our approach may help to improve ice core dating by: (1) revealing anomalies in accumulation-rate estimation based on the classical thermodynamic method and (2) supporting the necessity to take into account contributions due to changes in atmospheric circulation processes.
Keywords: 0325 Atmospheric Composition and Structure: Evolution of the atmosphere; 1620 Global Change: Climate dynamics; 1863 Hydrology: Snow and ice; 3344 Meteorology and Atmospheric Dynamics: Paleoclimatology; 9310 Information Related to Geographic Region: Antarctica
Programme: 960
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