References of "Geilfus, Nicolas-Xavier"
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See detailPhysical controls on the storage of methane in landfast sea ice
Zhou, Jiayun ULg; Tison, J.-L.; Carnat, G. et al

in The Cryosphere (2014), 8(3), 1019-1029

We report on methane (CH4) dynamics in landfast sea ice, brine and under-ice seawater at Barrow in 2009. The CH4 concentrations in under-ice water ranged between 25.9 and 116.4 nmol L-1sw, indicating a ... [more ▼]

We report on methane (CH4) dynamics in landfast sea ice, brine and under-ice seawater at Barrow in 2009. The CH4 concentrations in under-ice water ranged between 25.9 and 116.4 nmol L-1sw, indicating a supersaturation of 700 to 3100 % relative to the atmosphere. In comparison, the CH4 concentrations in sea ice, ranged between 3.4 and 17.2 nmol L-1ice, and the deduced CH4 concentrations in brine, between 13.2 and 677.7 nmol L-1brine. We investigated on the processes explaining the difference in CH4 concentrations between sea ice, brine and the under-ice water, and suggest that biological controls on the storage of CH4 in ice was minor in comparison to the physical controls. Two physical processes regulated the storage of CH4 in our landfast ice samples: bubble formation within the ice and sea ice permeability. Gas bubble formation from solubility changes had favoured the accumulation of CH4 in the ice at the beginning of ice growth. CH4 retention in sea ice was then twice as efficient as that of salt; this also explains the overall higher CH4 concentrations in brine than in the under-ice water. As sea ice thickened, gas bubble formation became less efficient, CH4 was then mainly trapped in the dissolved state. The increase of sea ice permeability during ice melt marked the end of CH4 storage. [less ▲]

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See detailFirst estimates of the contribution of CaCO3 precipitation to the release of CO2 to the atmosphere during young sea ice growth
Geilfus, Nicolas-Xavier ULg; Carnat, Gauthier; Dieckmann, G.S. et al

in Journal of Geophysical Research. Oceans (2013), 118(1-12), 244-255

We report measurements of pH, total alkalinity, air-ice CO2 fluxes (chamber method) and CaCO3 content of frost flowers (FF) and thin landfast sea ice. As the temperature decreases, concentration of ... [more ▼]

We report measurements of pH, total alkalinity, air-ice CO2 fluxes (chamber method) and CaCO3 content of frost flowers (FF) and thin landfast sea ice. As the temperature decreases, concentration of solutes in the brine skim (BS) increases. Along this gradual concentration process, some salts reach their solubility threshold and start precipitating. The precipitation of ikaite (CaCO3.6H2O) was confirmed in the FF and throughout the ice by Raman spectroscopy and X-ray analysis. The amount of ikaite precipitated was estimated to be 25 µmol kg-1 melted FF, in the FF and is shown to decrease from 19 µmol kg-1 to 15 µmol kg-1 melted ice in the upper part and at the bottom of the ice, respectively. CO2 release due to precipitation of CaCO3 is estimated to be 50 µmol kg-1 melted samples. The dissolved inorganic carbon (DIC) normalized to a salinity of 10 exhibits significant depletion in the upper layer of the ice and in the FF. This DIC loss is estimated to be 2069 µmol kg-1 melted sample and corresponds to a CO2 release from the ice to the atmosphere ranging from 20 to 40 mmol m-2 d-1. This estimate is consistent with flux measurements of air-ice CO2 exchange. Our measurements confirm previous laboratory findings that growing young sea ice acts as a source of CO2 to the atmosphere. CaCO3 precipitation during early ice growth appears to promote the release of CO2 to the atmosphere however its contribution to the overall release by newly formed ice is most likely minor. [less ▲]

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See detailInvestigations on physical and textural properties of Arctic first-year sea ice in the Amundsen Gulf, Canada, November 2007–June 2008 (IPY-CFL system study)
Carnat, Gauthier; Papakyriakou, Timothy; Geilfus, Nicolas-Xavier ULg et al

in Journal of Glaciology (2013), 59(217),

We report sea-ice temperature and bulk salinity measurements as well as textural analysis from 33 first-year drift- and fast-ice stations sampled between November 2007 and June 2008 in the southern ... [more ▼]

We report sea-ice temperature and bulk salinity measurements as well as textural analysis from 33 first-year drift- and fast-ice stations sampled between November 2007 and June 2008 in the southern Beaufort Sea–Amundsen Gulf, Canadian Arctic, during the International Polar Year Circumpolar Flaw Lead (IPY-CFL) system study. We use this significant dataset to investigate the halothermodynamic evolution of sea ice from growth to melt. A strong desalination phase is observed over a small time window in the spring. Using calculated proxies of sea-ice permeability (brine volume fraction) and of the intensity of brine convection (Rayleigh number) we demonstrate that this phase corresponds to full-depth gravity drainage initiated by a restored connectivity of the brine network with warming in the spring. Most stations had a textural sequence typical of Arctic first-year ice, with granular ice overlying columnar ice. Unusual textural features were observed sporadically: sandwiched granular ice, platelet ice and draped platelet ice. We suggest that turbulence in leads and double diffusion in strong brine plumes following the refreeze of cracks are plausible mechanisms for the formation of these textures. [less ▲]

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See detailPhysical and biogeochemical properties in landfast sea ice (Barrow, Alaska): insights on brine and gas dynamics across seasons
Zhou, Jiayun ULg; Delille, Bruno ULg; Eicken, H. et al

in Journal of Geophysical Research (2013), 118(6), 3172-3189

The impacts of the seasonal evolution of sea-ice physical properties on ice-ocean biogeochemical exchanges were investigated in landfast ice at Barrow (Alaska) from January through June 2009. Three stages ... [more ▼]

The impacts of the seasonal evolution of sea-ice physical properties on ice-ocean biogeochemical exchanges were investigated in landfast ice at Barrow (Alaska) from January through June 2009. Three stages of brine dynamics across the annual cycle have been identified based on brine salinity, brine volume fraction and porous medium Rayleigh number [less ▲]

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See detailInorganic carbon dynamics in coastal arctic sea ice and related air-ice CO2 exchanges
Geilfus, Nicolas-Xavier ULg; Tison, J.-L.; Carnat, G. et al

Poster (2012, April)

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See detailDynamics of pCO2 and related air-ice CO2 fluxes in the Arctic coastal zone (Amundsen Gulf, Beaufort Sea)
Geilfus, Nicolas-Xavier ULg; Carnat, G.; Papakyriakou, T. et al

in Journal of Geophysical Research. Oceans (2012), 117(C00G10),

We present an Arctic seasonal survey of carbon dioxide partial pressure (pCO2) dynamics within sea ice brine and related air-ice CO2 fluxes. The survey was carried out from early spring to the beginning ... [more ▼]

We present an Arctic seasonal survey of carbon dioxide partial pressure (pCO2) dynamics within sea ice brine and related air-ice CO2 fluxes. The survey was carried out from early spring to the beginning of summer in the Arctic coastal waters of the Amundsen Gulf. High concentrations of pCO2 (up to 1834 matm) were observed in the sea ice in early April as a consequence of concentration of solutes in brines, CaCO3 precipitation and microbial respiration. CaCO3 precipitation was detected through anomalies in total alkalinity (TA) and dissolved inorganic carbon (DIC). This precipitation seems to have occurred in highly saline brine in the upper part of the ice cover and in bulk ice. As summer draws near, the ice temperature increases and brine pCO2 shifts from a large supersaturation (1834 matm) to a marked undersaturation (down to almost 0 matm). This decrease was ascribed to brine dilution by ice meltwater, dissolution of CaCO3 and photosynthesis during the sympagic algal bloom. The magnitude of the CO2 fluxes was controlled by ice temperature (through its control on brine volume and brine channels connectivity) and the concentration gradient between brine and the atmosphere. However, the state of the ice-interface clearly affects air-ice CO2 fluxes. [less ▲]

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See detailTowards a method for high vertical resolution measurements of the partial pressure of CO2 within bulk sea ice
Geilfus, Nicolas-Xavier ULg; Delille, Bruno ULg; Verbeke, Véronique et al

in Journal of Glaciology (2012), 58(208), 287-300

Fluxes of atmospheric CO2 have been reported over sea ice during winter and spring. These fluxes are partly driven by the gradient of the CO2 concentration between sea ice and the atmosphere. We present a ... [more ▼]

Fluxes of atmospheric CO2 have been reported over sea ice during winter and spring. These fluxes are partly driven by the gradient of the CO2 concentration between sea ice and the atmosphere. We present a new non-destructive method to measure the pCO2 of bulk sea ice at its in situ temperature. This method is based on an equilibration procedure between sea ice and a standard gas of known CO2 concentration. The concentration is measured by gas chromatography with a precision of 5%. Tests were performed on artificial standard sea ice and confirmed the reproducibility of the technique in the range of precision of the gas chromatograph. To test the accuracy of this method, the first profiles of pCO2 measured in bulk sea ice are reported and compared with direct in situ measurements of brine pCO2 over depth-integrated intervals. [less ▲]

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See detailO2/Ar and CH4 measurements in sea ice : clues for the key status of sea ice in the climate system
Zhou, Jiayun; Tison, Jean-Louis; Eicken, Hajo et al

in Geophysical Research Abstracts (2011, April 08), 13

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See detailTemporal evolution of biogeochemical properties of landfast sea ice at Barrow (Alaska)
Zhou, Jiayun ULg; Tison, Jean-Louis; Eicken, Hajo et al

Poster (2011, March)

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See detailA multidisciplinary approach to understanding the sea ice system: implications on gas. Gordon Research Seminars
Zhou, Jiayun ULg; Tison, Jean-Louis; Eicken, Hajo et al

Conference (2011, March)

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See detailOverview of CO2 dynamics within sea ice
Delille, Bruno ULg; Geilfus, Nicolas-Xavier ULg; Vancoppenolle, M. et al

Conference (2011)

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See detailDynamic processes in sea ice captured by the temporal evolution of its biogeochemical
Zhou, Jiayun; Tison, Jean-Louis; Eicken, Hajo et al

in VLIZ Special Publication (2011), 48

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See detailAir-ice CO2 fluxes and pCO2 dynamics in sea ice in the Arctic coastal area (Amundsen Gulf, Canada)
Geilfus, Nicolas-Xavier ULg; Tison, Jean Louis; Carnat, Gauthier et al

Conference (2010, May)

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See detailAir-sea ice CO2 fluxes measurement with eddy-covariance micrometeorological technique
Heinesch, Bernard ULg; Aubinet, Marc ULg; Carnat, Gauthier et al

Conference (2010, April)

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See detailMicrometeorological survey of air-sea ice CO2 fluxes in arctic coastal waters
Heinesch, Bernard ULg; Tison, Jean-Louis; Carnat, Gauthier et al

in Geophysical Research Abstracts (2010), 12(EGU2010-10570),

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See detailOceanic CO2 sink: the contribution of the marine cryosphere
Delille, Bruno ULg; Vancoppenolle, M.; Tilbrook, B. et al

Conference (2010)

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See detailpCO2 in sea ice and CO2 fluxes estimates: where do we stand today?
Tison, J.; Delille, Bruno ULg; Papakyriakou, T. N. et al

Conference (2009, December)

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See detailSpatiotemporal variations of DMSO in arctic sea ice: new insights using dmso reductase enzyme
Carnat, Gauthier; Brabant, Frederic; Papakyriakou, Tim et al

Poster (2009, November)

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See detailAir-ice CO2 fluxes and pCO2 dynamics in sea ice in the Arctic (Amundsen Gulf)
Geilfus, Nicolas-Xavier ULg; Tison, Jean Louis; Carnat, Gauthier et al

Conference (2009, November)

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