References of "Tison, Jean-Louis"
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See detailAir-ice carbon pathways inferred from a sea ice tank experiment
Kotovitch, Marie ULg; Moreau, Sébastien; Zhou, Jiayun et al

in Elementa: Science of the Anthropocene (2016)

Air-ice CO2 fluxes were measured continuously using automated chambers from the initial freezing of a sea ice cover until its decay. Cooling seawater prior to sea ice formation acted as a sink for ... [more ▼]

Air-ice CO2 fluxes were measured continuously using automated chambers from the initial freezing of a sea ice cover until its decay. Cooling seawater prior to sea ice formation acted as a sink for atmospheric CO2, but as soon as the first ice crystals started to form, sea ice turned to a source of CO2, which lasted throughout the whole ice growth phase. Once ice decay was initiated by warming the atmosphere, the sea ice shifted back again to a sink of CO2. Direct measurements of outward ice-atmosphere CO2 fluxes were consistent with the depletion of dissolved inorganic carbon in the upper half of sea ice. Combining measured air-ice CO2 fluxes with the partial pressure of CO2 in sea ice, we determined strongly different gas transfer coefficients of CO2 at the air-ice interface between the growth and the decay phases (from 2.5 to 0.4 mol m−2 d−1 atm−1). A 1D sea ice carbon cycle model including gas physics and carbon biogeochemistry was used in various configurations in order to interpret the observations. All model simulations correctly predicted the sign of the air-ice flux. By contrast, the amplitude of the flux was much more variable between the different simulations. In none of the simulations was the dissolved gas pathway strong enough to explain the large fluxes during ice growth. This pathway weakness is due to an intrinsic limitation of ice-air fluxes of dissolved CO2 by the slow transport of dissolved inorganic carbon in the ice. The best means we found to explain the high air-ice carbon fluxes during ice growth is an intense yet uncertain gas bubble efflux, requiring sufficient bubble nucleation and upwards rise. We therefore call for further investigation of gas bubble nucleation and transport in sea ice. [less ▲]

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See detailContrasting Arctic and Antarctic sea ice temperatures
Vancoppenolle, M.; Raphael, M.; Rousset, C. et al

Conference (2016, April)

Sea ice temperature affects the sea ice growth rate, heat content, permeability and habitability for ice algae. Large-scale simulations with NEMO-LIM suggest large ice temperature contrasts between the ... [more ▼]

Sea ice temperature affects the sea ice growth rate, heat content, permeability and habitability for ice algae. Large-scale simulations with NEMO-LIM suggest large ice temperature contrasts between the Arctic and the Antarctic sea ice. First, Antarctic sea ice proves generally warmer than in the Arctic, in particular during winter, where differences reach up to ∼10◦C. Second, the seasonality of temperature is different among the two hemispheres: Antarctic ice temperatures are 2-3◦C higher in spring than they are in fall, whereas the opposite is true in the Arctic. These two key differences are supported by the available ice core and mass balance buoys temperature observations, and can be attributed to differences in air temperature and snow depth. As a result, the ice is found to be habitable and permeable over much larger areas and much earlier in late spring in the Antarctic as compared with the Arctic, which consequences on biogeochemical exchanges in the sea ice zone remain to be evaluated. [less ▲]

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See detailULB-ULg: Seaicebiogeochemistryworkplan
Kotovitch, Marie ULg; Van Der Linden, Fanny ULg; Tison, Jean-Louis et al

Scientific conference (2016, March 16)

1. Manuscript submitted to Elementa Last year we submitted a manuscript about air-ice CO2 fluxes measured in continuous with a chamber over the ice during INTERICE V experiment. The results show that sea ... [more ▼]

1. Manuscript submitted to Elementa Last year we submitted a manuscript about air-ice CO2 fluxes measured in continuous with a chamber over the ice during INTERICE V experiment. The results show that sea ice shifts from: (i) a sink during ice crystals formation, (ii) a source during ice growth, (iii) return to a sink during ice melt. We attempt to reproduce these fluxes with the 1Dimension model developed by Martin and Sebastien in Moreau et al. (2015). The inversion between outward CO2 fluxes during ice growth and inward CO2 fluxes during ice melt depicts well the observations. However, the model strongly underestimates the fluxes during the cold phase if the formation rate of gas bubbles is low. Since ice is permeable throughout the cold phase, higher gas bubble formation rates lead to higher CO2 fluxes. The contribution of gas bubble buoyancy to upward flux was the main hypothesis of this manuscript. 2. TA-DIC compilation With the code developed by Martin (and others), we computed profile of DIC normalized to the mean ice salinity. We observe a reverse C shape with a depletion at the surface and more scattered data at the bottom. It’s striking to observe that at mid-depth (0.5 m), all data sounds to converge at the same value (around 480 µmol/kg). It makes us confident with the fact that we can gather data and compare them. The mean DIC value in the middle of the cores is similar to the sea surface water DIC in Antarctica. Our idea is that these value are due to simple brine rejection and that there is a depletion at the top and at the bottom. The bottom depletion is subject to biogeochemistry processes. While the top depletion may be due to the CO2 release during ice formation which lead to a potential CO2 flux out of the ice. For the time beeing, we aim to derive a budget of CO2 flux from this compilation. This will be presented at the next BEPSII meeting. 3. Further studies and perspectives (PhD thesis of Fanny and Marie) Sea ice production of N2O and halocarbons and their contribution to atmospheric concentrations. Development of a flux chamber in process. [less ▲]

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See detailNitrous oxide dynamics in sea ice
Kotovitch, Marie ULg; Fripiat, François ULg; Moreau, Sébastien et al

Conference (2016, February 26)

Fluctuations in greenhouse gases (GHGs) concentration alter the energetic budget of the climate system. There is high confidence that natural systems related to snow, ice and frozen ground (including ... [more ▼]

Fluctuations in greenhouse gases (GHGs) concentration alter the energetic budget of the climate system. There is high confidence that natural systems related to snow, ice and frozen ground (including permafrost) are affected. Nitrous oxide (N2O) is one of the potent GHG naturally present in the atmosphere, but witch has seen his concentration growing since industrial era. N2O has a lifetime in the atmosphere of 114 years and a global warming potential (GWP) of 298 to be compared to carbon dioxide that has a GWP of 1. N2O is also describe as the dominant ozone-depleting substance emitted in the 21st Century. Yet, there are still large uncertainties and gaps in the understanding of the cycle of this compound through the ocean and particularly in sea ice. Sources and sinks of N2O are therefore still poorly quantified. The main processes (with the exception of transport processes) involved in the N2O cycle within the aquatic environment are nitrification and denitrification. To date, only one study by Randall et al. present N2O measurements in sea ice. Randall et al. pointed out that sea ice formation and melt has the potential to generate sea-air or air-sea fluxes of N2O, respectively. [less ▲]

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See detailAnnual dynamics of pCO2 within bulk sea ice and related CO2 fluxes at Cape Evans (Antarctica)
Van Der Linden, Fanny ULg; Champenois, Willy ULg; Heinesch, Bernard ULg et al

Poster (2016, February 26)

Sea ice is a biome actively participating in the regional cycling of CO2 as both a source and a sink at different times of the year. In the frame of the YROSIAE project (Year-Round Ocean-Sea-Ice ... [more ▼]

Sea ice is a biome actively participating in the regional cycling of CO2 as both a source and a sink at different times of the year. In the frame of the YROSIAE project (Year-Round Ocean-Sea-Ice-Atmosphere Exchanges), annual dynamics of sea ice pCO2 was compared with CO2 fluxes measured by automated accumulation chambers at Cape Evans (Ross Island, Antarctica). Results confirmed a general trend of brine pCO2 supersaturation with respect to the atmosphere during the late winter (concentration of dissolved inorganic carbon - DIC - in brine and brine expulsion in the brine skim) leading to CO2 degassing, and undersaturation during the spring (carbon-uptake by autotrophs and brine dilution) leading to atmospheric CO2 uptake. Despite high primary production at the bottom of the ice in spring, DIC profiles suggest that sea ice as a whole appears to be net heterotrophic. Still, sea ice absorbs CO2 from the atmosphere, as a result of physical processes. Some variability in the CO2 fluxes (both in magnitude and sign) could not be explained by variability in sea ice pCO2 but rather seemed driven by variability in atmospheric conditions and sea ice surface properties. For instance, in late spring, CO2 fluxes showed a diurnal variability (from CO2 degassing to uptake) related to atmospheric temperature variations. Large and episodic CO2 fluxes were systematically positively correlated with strong wind events, and large CO2 degassing was observed over thin, wet and salty snow cover. [less ▲]

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See detailAnnual dynamics of pCO2 within bulk sea ice and related CO2 fluxes at Cape Evans (Antarctica)
Van Der Linden, Fanny ULg; Champenois, Willy ULg; Heinesch, Bernard ULg et al

Poster (2016, February 12)

Sea ice is a biome actively participating in the regional cycling of CO2 as both a source and a sink at different times of the year. In the frame of the YROSIAE project (Year-Round Ocean-Sea-Ice ... [more ▼]

Sea ice is a biome actively participating in the regional cycling of CO2 as both a source and a sink at different times of the year. In the frame of the YROSIAE project (Year-Round Ocean-Sea-Ice-Atmosphere Exchanges), annual dynamics of sea ice pCO2 was compared with CO2 fluxes measured by automated accumulation chambers at Cape Evans (Ross Island, Antarctica). Results confirmed a general trend of brine pCO2 supersaturation with respect to the atmosphere during the late winter (concentration of dissolved inorganic carbon - DIC - in brine and brine expulsion in the brine skim) leading to CO2 degassing, and undersaturation during the spring (carbon-uptake by autotrophs and brine dilution) leading to atmospheric CO2 uptake. Despite high primary production at the bottom of the ice in spring, DIC profiles suggest that sea ice as a whole appears to be net heterotrophic. Still, sea ice absorbs CO2 from the atmosphere, as a result of physical processes. Some variability in the CO2 fluxes (both in magnitude and sign) could not be explained by variability in sea ice pCO2 but rather seemed driven by variability in atmospheric conditions and sea ice surface properties. For instance, in late spring, CO2 fluxes showed a diurnal variability (from CO2 degassing to uptake) related to atmospheric temperature variations. Large and episodic CO2 fluxes were systematically positively correlated with strong wind events, and large CO2 degassing was observed over thin, wet and salty snow cover. [less ▲]

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See detailNitrous oxide dynamics in sea ice
Kotovitch, Marie ULg; Fripiat, François; Moreau, Sebastien et al

Poster (2016, February 12)

Fluctuations in greenhouse gases (GHGs) concentration alter the energetic budget of the climate system. There is high confidence that natural systems related to snow, ice and frozen ground (including ... [more ▼]

Fluctuations in greenhouse gases (GHGs) concentration alter the energetic budget of the climate system. There is high confidence that natural systems related to snow, ice and frozen ground (including permafrost) are affected. Nitrous oxide (N2O) is one of the potent GHG naturally present in the atmosphere, but witch has seen his concentration growing since industrial era. N2O has a lifetime in the atmosphere of 114 years and a global warming potential (GWP) of 298 to be compared to carbon dioxide that has a GWP of 1. N2O is also describe as the dominant ozone-depleting substance emitted in the 21st Century. Yet, there are still large uncertainties and gaps in the understanding of the cycle of this compound through the ocean and particularly in sea ice. Sources and sinks of N2O are therefore still poorly quantified. The main processes (with the exception of transport processes) involved in the N2O cycle within the aquatic environment are nitrification and denitrification. To date, only one study by Randall et al. present N2O measurements in sea ice. Randall et al. pointed out that sea ice formation and melt has the potential to generate sea-air or air-sea fluxes of N2O, respectively. Study on ammonium oxidation and anaerobic bacterial cultures shows that N2O production can potentially occur in sea ice. Denitrification can act as a sink or a source of N2O. In strictly anaerobic conditions, N2O is removed by denitrification. However, denitrification can also occur in presence of O2 at trace level concentrations (<0.2 mg L-1), and in these conditions there is a large N2O production. Recent observations of significant nitrification in Antarctic sea ice shed a new light on nitrogen cycle within sea ice. It has been suggested that nitrification supplies up to 70% of nitrate assimilated within Antarctic spring sea ice. Corollary, production of N2O, a by-product of nitrification, can potentially be significant. This was recently confirmed in Antarctic land fast ice in McMurdo Sound, where N2O release to the atmosphere was estimated to 4 µmol.m-2.yr-1. This assessment is probably an underestimate since it only accounts for dissolved N2O while a significant amount of N2O is likely to occur in the gaseous form like N2, O2 and Ar. Finally, nitrification produces little N2O in oxygenated waters but the N2O production yield from nitrification strongly increases as O2 levels decrease. Hence, it is not possible to distinguish the sources of N2O solely based on bulk N2O concentrations or environmental conditions, while deepened knowledge of processes is needed to well understand N2O emissions. [less ▲]

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See detailYear Round Survey of Ocean-Sea Ice-Air Exchanges – the YROSIAE survey
Delille, Bruno ULg; Van Der Linden, Fanny ULg; Fripiat, François et al

Poster (2015, September 08)

YROSIAE survey aimed to carry out a year-round integrated survey of land-fast sea ice focusing on the study of sea ice physics and biogeochemistry in order to a) better understand and budget exchanges of ... [more ▼]

YROSIAE survey aimed to carry out a year-round integrated survey of land-fast sea ice focusing on the study of sea ice physics and biogeochemistry in order to a) better understand and budget exchanges of energy and matter across the ocean-sea ice-atmosphere interfaces during sea ice growth and decay and b) quantify their potential impact on fluxes of climate gases (CO2, DMS, CH4, N2O) to the atmosphere and on carbon and macro- nutrients and micro-nutrients export to the ocean. We will present the aims, overall approach and integrated sampling strategy of the YROSIAE survey. We will also discuss CO2 and N2O dynamics within sea ice. It appears that sea ice acts as a source of CO2 for the atmosphere in winter, counterbalancing spring sink. In addition, mineralization in spring appears to alleviate spring CO2 uptake. Intense nitrification in sea ice in spring fosters emission of N2O at the air-ice interface. [less ▲]

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See detailThe study of air-ice CO2 exchange emphasize the importance of gas bubble transport during sea ice growth
Kotovitch, Marie ULg; Moreau, Sébastien; Zhou, Jiayun et al

Poster (2015, August 20)

We report air-ice CO2 fluxes measured continuously using automated chambers over artificial sea ice from freezing to decay. We observed an uptake of CO2 as seawater was cooling down prior to sea ice ... [more ▼]

We report air-ice CO2 fluxes measured continuously using automated chambers over artificial sea ice from freezing to decay. We observed an uptake of CO2 as seawater was cooling down prior to sea ice formation. As soon as the first ice crystals started to form, we observed a shift from a sink to a source. Sea ice released CO2 until we initiated the ice decay by warming the atmosphere. Sea ice then returned to be a CO2 sink. Direct measurements of the fluxes were consistent with the depletion of dissolved inorganic carbon in sea ice. Measurements of bulk partial pressure of CO2 in sea ice and of atmospheric CO2 allowed us to assess a gas exchange coefficient for CO2 at the air-sea ice interface during the grow stage. We compared these observations with a 1D biogeochemical model. Discrepancies between the model and the observations lead us to emphasize the role of gas bubbles in CO2 transport through sea ice. [less ▲]

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See detailMeasurements of air-ice CO2 fluxes over artificial sea ice emphasize the role of bubbles in gas transport
Kotovitch, Marie ULg; Moreau, Sébastion; Zhou, Jiayun et al

Poster (2015, March)

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See detailDrivers of inorganic carbon dynamics in first-year sea ice: A model study.
Moreau, Sebastien; Vancoppenolle, Martin; Delille, Bruno ULg et al

in Journal of Geophysical Research. Oceans (2015), 120

Sea ice is an active source or a sink for carbon dioxide (CO2), although to what extent is not clear. Here, we analyze CO2 dynamics within sea ice using a one-dimensional halo-thermodynamic sea ice model ... [more ▼]

Sea ice is an active source or a sink for carbon dioxide (CO2), although to what extent is not clear. Here, we analyze CO2 dynamics within sea ice using a one-dimensional halo-thermodynamic sea ice model including gas physics and carbon biogeochemistry. The ice-ocean fluxes and vertical transport of total dissolved inorganic carbon (DIC) and total alkalinity (TA) are represented using fluid transport equations. [less ▲]

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See detailPhysical and bacterial controls on inorganic nutrients and dissolved organic carbon during a sea ice growth and decay experiment
Zhou, Jiayun ULg; Delille, Bruno ULg; Kaartokallio, Hermanni et al

in Marine Chemistry (2014), 166

We investigated how physical incorporation, brine dynamics and bacterial activity regulate the distribution of inorganic nutrients and dissolved organic carbon (DOC) in artificial sea ice during a 19-day ... [more ▼]

We investigated how physical incorporation, brine dynamics and bacterial activity regulate the distribution of inorganic nutrients and dissolved organic carbon (DOC) in artificial sea ice during a 19-day experiment that included periods of both ice growth and decay. The experiment was performed using two series of mesocosms: the first consisted of seawater and the second consisted of seawater enriched with humic-rich river water. We grew ice by freezing the water at an air temperature of -14 °C for 14 days after which ice decay was induced by increasing the air temperature to -1 °C. Using the ice temperatures and bulk ice salinities, we derived the brine volume fractions, brine salinities and Rayleigh numbers. The temporal evolution of these physical parameters indicate that there was a succession of 3 stages in the brine dynamics: forced-convection, followed by bottom convection during ice growth, and then brine stratification during ice decay. The major findings are: (1) the incorporation of dissolved compounds (nitrate, nitrite, ammonium, phosphate, silicate, and DOC) into the sea ice was not conservative (relative to salinity) during ice growth. Brine convection clearly influenced the incorporation of the dissolved compounds, since the non-conservative behavior of the dissolved compounds was particularly pronounced in the absence of brine convection. (2) Bacterial activity further regulated nutrient availability in the ice: ammonium and nitrite accumulated as a result of remineralization processes, although bacterial production was too low to induce major changes in DOC concentrations. (3) Different forms of DOC have different properties and hence incorporation efficiencies. In particular, the terrestrially-derived DOC from the river water was less efficiently incorporated into sea ice than the DOC in the seawater. Therefore the main factors regulating the distribution of the dissolved compounds within sea ice are clearly a complex interaction of brine dynamics, biological activity and in the case of dissolved organic matter, the physico-chemical properties of the dissolved constituents themselves. [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 detailBiogenic silica recycling in sea ice inferred from Si-isotopes: constraints from Arctic winter first-year sea ice
Fripiat, François; Tison, Jean-Louis; André, Luc et al

in Biogeochemistry (2013)

We report silicon isotopic composition (d30Si vs. NBS28) in Arctic sea ice, based on sampling of silicic acid from both brine and seawater in a small Greenlandic bay in March 2010. Our measurements show ... [more ▼]

We report silicon isotopic composition (d30Si vs. NBS28) in Arctic sea ice, based on sampling of silicic acid from both brine and seawater in a small Greenlandic bay in March 2010. Our measurements show that just before the productive period, d30Si of sea-ice brine similar to d30Si of the underlying seawater. Hence, there is no Si isotopic fractionation during sea-ice growth by physical processes such as brine convection. This finding brings credit and support to the conclusions of previous work on the impact of biogenic processes on sea ice d30Si: any d30Si change results from a combination of biogenic silica production and dissolution. We use this insight to interpret data from an earlier study of sea-ice d30Si in Antarctic pack ice that show a large accumulation of biogenic silica. Based on these data, we estimate a significant contribution of biogenic silica dissolution (D) to production (P), with a D:P ratio between 0.4 and 0.9. This finding has significant implications for the understanding and parameterization of the sea ice Sibiogeochemical cycle, i.e. previous studies assumed little or no biogenic silica dissolution in sea ice. [less ▲]

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See detailGas migration in sea ice: from observations to modelling
Zhou, Jiayun ULg; Moreau, Sébastien; Vancoppenolle, Martin et al

Poster (2012, May 07)

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See detailFluxes of dimethylsulfide from warming sea ice
Carnat, Gauthier; Zhou, Jiayun; Papakyriakou, Tim et al

Poster (2012, May)

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See detailSea ice as a source of bioavailable iron to the Southern Ocean
Schoemann, Véronique; Lannuzel, Delphine; de Jong et al

Conference (2012, May)

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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 detailSea ice contribution to the air-sea CO2 exchange in the Arctic and Southern Oceans
Rysgaard, Søren; Bendtsen; Delille, Bruno ULg et al

in Tellus : Series B (2011), 63(5), 823-830

Although salt rejection from sea ice is a key process in deep-water formation in ice-covered seas, the concurrent rejection of CO2 and the subsequent effect on air–sea CO2 exchange have received little ... [more ▼]

Although salt rejection from sea ice is a key process in deep-water formation in ice-covered seas, the concurrent rejection of CO2 and the subsequent effect on air–sea CO2 exchange have received little attention. We review the mechanisms by which sea ice directly and indirectly controls the air–sea CO2 exchange and use recent measurements of inorganic carbon compounds in bulk sea ice to estimate that oceanic CO2 uptake during the seasonal cycle of sea-ice growth and decay in ice-covered oceanic regions equals almost half of the net atmospheric CO2 uptake in ice-free polar seas. This sea-ice driven CO2 uptake has not been considered so far in estimates of global oceanic CO2 uptake. Net CO2 uptake in sea-ice–covered oceans can be driven by; (1) rejection during sea–ice formation and sinking of CO2-rich brine into intermediate and abyssal oceanic water masses, (2) blocking of air–sea CO2 exchange during winter, and (3) release of CO2-depleted melt water with excess total alkalinity during sea-ice decay and (4) biological CO2 drawdown during primary production in sea ice and surface oceanic waters. [less ▲]

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