References of "Heinesch, Bernard"
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See detailComment l'agriculture peut-elle contribuer à limiter les changements climatiques? Contribution de la recherche.
Heinesch, Bernard ULg; Aubinet, Marc ULg; Dehareng, Frédéric et al

Conference given outside the academic context (2015)

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See detailInterpreting canopy development and physiology using a European phenology camera network at flux sites
Wingate, L.; Ogée, J.; Cremonese, E. et al

in Biogeosciences (2015), 12(10), 5995-6015

Plant phenological development is orchestrated through subtle changes in photoperiod, temperature, soil moisture and nutrient availability. Presently, the exact timing of plant development stages and ... [more ▼]

Plant phenological development is orchestrated through subtle changes in photoperiod, temperature, soil moisture and nutrient availability. Presently, the exact timing of plant development stages and their response to climate and management practices are crudely represented in land surface models. As visual observations of phenology are laborious, there is a need to supplement long-term observations with automated techniques such as those provided by digital repeat photography at high temporal and spatial resolution. We present the first synthesis from a growing observational network of digital cameras installed on towers across Europe above deciduous and evergreen forests, grasslands and croplands, where vegetation and atmosphere CO2 fluxes are measured continuously. Using colour indices from digital images and using piecewise regression analysis of time series, we explored whether key changes in canopy phenology could be detected automatically across different land use types in the network. The piecewise regression approach could capture the start and end of the growing season, in addition to identifying striking changes in colour signals caused by flowering and management practices such as mowing. Exploring the dates of green-up and senescence of deciduous forests extracted by the piecewise regression approach against dates estimated from visual observations, we found that these phenological events could be detected adequately (RMSE < 8 and 11 days for leaf out and leaf fall, respectively). We also investigated whether the seasonal patterns of red, green and blue colour fractions derived from digital images could be modelled mechanistically using the PROSAIL model parameterised with information of seasonal changes in canopy leaf area and leaf chlorophyll and carotenoid concentrations. From a model sensitivity analysis we found that variations in colour fractions, and in particular the late spring `green hump' observed repeatedly in deciduous broadleaf canopies across the network, are essentially dominated by changes in the respective pigment concentrations. Using the model we were able to explain why this spring maximum in green signal is often observed out of phase with the maximum period of canopy photosynthesis in ecosystems across Europe. Coupling such quasi-continuous digital records of canopy colours with co-located CO2 flux measurements will improve our understanding of how changes in growing season length are likely to shape the capacity of European ecosystems to sequester CO2 in the future. [less ▲]

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See detailSetting up an eddy covariance system to measure N2O fluxes exchanged by a production crop - First steps
Lognoul, Margaux ULg; SALERNO, Giovanni ULg; Debacq, Alain ULg et al

Poster (2015, October 20)

In order to study N2O exchanges by a Belgian production crop, we installed an eddy covariance system at the Terrestrial Observatory of Lonzée (Belgium), using a H2O and N2O quantum cascade laser analyzer ... [more ▼]

In order to study N2O exchanges by a Belgian production crop, we installed an eddy covariance system at the Terrestrial Observatory of Lonzée (Belgium), using a H2O and N2O quantum cascade laser analyzer and a sonic anemometer. We obtained three days of measurements and were able to investigate data preprocessing and flux calculation. We observed a drifting time-lag between the analyzer and the anemometers time series, presumably caused by an internal clock drift. Time-lag determination (using the covariance function maximum method) was more difficult for N2O than H2O, suggesting that this routine should be adapted to gas characterized by low fluxes. We investigated high frequency loss and found a system cut-off frequency of 0.5Hz for H2O, comparing its cospectrum to sensible heat cospectrum. We were not able to retrieve a neat cospectrum for N2O because of low fluxes during turbulent conditions. Further work and more data will be needed in order to bring answers to pending questions. [less ▲]

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See detailAir-sea ice gases exchange: update of recent findings, outcomes from sea ice models, caveats and open questions
Delille, Bruno ULg; Zhou, Jiayun; Kotovitch, Marie ULg et al

Conference (2015, September 21)

There are growing evidences that sea ice exchanges climate gases with the atmosphere. We will rapidly present a state of the art of current large scale assessment of spring and summer uptake of ... [more ▼]

There are growing evidences that sea ice exchanges climate gases with the atmosphere. We will rapidly present a state of the art of current large scale assessment of spring and summer uptake of atmospheric CO2. We will challenge these assessments with 1) new evidence of significant winter CO2 release for winter experiments 2) new finding of the role of bubbles formation and transport within sea ice and 3) impurities expulsion derived from combined artificial ice experiment and modelling. Finally, comparison of air-ice fluxes derived from automated chamber and micrometeorological method and, mechanistic and box models show significant discrepancies that suggest that the contribution of sea ice to the air-ocean fluxes of CO2 remain an open question. We will also highlight that sea ice contribute to the fluxes of other gases as CH4 ,N2O and DMS [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 detailAn ecosystem-scale perspective of the net land methanol flux: synthesis of micrometeorological flux measurements
Wohlfahrt, G.; Amelynck, C.; Ammann, C. et al

in Atmospheric Chemistry and Physics (2015), (15), 7413-7427

Methanol is the second most abundant volatile organic compound in the troposphere and plays a significant role in atmospheric chemistry. While there is consensus about the dominant role of living plants ... [more ▼]

Methanol is the second most abundant volatile organic compound in the troposphere and plays a significant role in atmospheric chemistry. While there is consensus about the dominant role of living plants as the major source and the reaction with OH as the major sink of methanol, global methanol budgets diverge considerably in terms of source/sink estimates, reflecting uncertainties in the approaches used to model and the empirical data used to separately constrain these terms. Here we compiled micrometeorological methanol flux data from eight different study sites and reviewed the corresponding literature in order to provide a first cross-site synthesis of the terrestrial ecosystem-scale methanol exchange and present an independent data-driven view of the land–atmosphere methanol exchange. Our study shows that the controls of plant growth on production, and thus the methanol emission magnitude, as well as stomatal conductance on the hourly methanol emission variability, established at the leaf level, hold across sites at the ecosystem level. Unequivocal evidence for bi-directional methanol exchange at the ecosystem scale is presented. Deposition, which at some sites even exceeds methanol emissions, represents an emerging feature of ecosystem-scale measurements and is likely related to environmental factors favouring the formation of surface wetness. Methanol may adsorb to or dissolve in this surface water and eventually be chemically or biologically removed from it. Management activities in agriculture and forestry are shown to increase local methanol emission by orders of magnitude; however, they are neglected at present in global budgets. While contemporary net land methanol budgets are overall consistent with the grand mean of the micrometeorological methanol flux measurements, we caution that the present approach of simulating methanol emission and deposition separately is prone to opposing systematic errors and does not allow for full advantage to be taken of the rich information content of micrometeorological flux measurements. [less ▲]

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See detailCritical periods and critical values explaining fluxes inter-annual variability in a temperate mixed forest
Hurdebise, Quentin ULg; Vincke, Caroline; De Ligne, Anne ULg et al

Poster (2015, June 04)

In order to explain inter-annual variability of Net Ecosystem CO2 Exchange (NEE) above a mixed temperate forest, two approaches were followed: •Detection of critical periods using the R-squared of the ... [more ▼]

In order to explain inter-annual variability of Net Ecosystem CO2 Exchange (NEE) above a mixed temperate forest, two approaches were followed: •Detection of critical periods using the R-squared of the regression between annual NEE and cumulated NEE on a mobile window. •Identification of critical values of a threshold used to decompose annual and seasonal NEE in two components. [less ▲]

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See detailThe CROSTVOC project – an integrated approach to study the effect of stress on BVOC exchange between agricultural crops and grassland ecosystems and the atmosphere
Amelynck, Crist; Heinesch, Bernard ULg; Aubinet, Marc ULg et al

in Geophysical Research Abstracts (2015, April), 17

Global changes in atmospheric composition and climate are expected to affect BVOC exchange between terrestrial vegetation and the atmosphere through changes in the drivers of constitutive BVOC emissions ... [more ▼]

Global changes in atmospheric composition and climate are expected to affect BVOC exchange between terrestrial vegetation and the atmosphere through changes in the drivers of constitutive BVOC emissions and by increases in frequency and intensity of biotic or abiotic stress episodes. Indeed, several studies indicate changes in the emission patterns of constitutive BVOCs and emission of stress-induced BVOCs following heat, drought and oxidative stress, amongst others. Relating changes in BVOC emissions to the occurrence of one or multiple stressors in natural environmental conditions is not straightforward and only few field studies have dealt with it, especially for agricultural crop and grassland ecosystems. The CROSTVOC project aims to contribute in filling this knowledge gap in three ways. Firstly, it aims at performing long-term BVOC emission field measurements from maize (Zea mays L.) and wheat (Triticum aestivum L.), two important crop species on the global scale, and from grassland. This should lead to a better characterization of (mainly oxygenated) BVOC emissions from these understudied ecosystems, allowing a better representation of those emissions in air quality and atmospheric chemistry and transport models. BVOC fluxes are obtained by the Disjunct Eddy Covariance by mass scanning (DEC-MS) technique, using a hs-PTR-MS instrument for BVOC analysis. Secondly, the eddy covariance BVOC flux measurements (especially at the grassland site) will be accompanied by ozone flux, chlorophyll fluorescence, photosynthesis and soil moisture measurements, amongst others, to allow linking alterations in BVOC emissions to stress episodes. Simultaneously, automated dynamic enclosures will be deployed in order to detect specific abiotic and biotic stress markers by PTR-MS and identify them unambiguously by GC-MS. Thirdly, the field measurements will be accompanied by laboratory BVOC flux measurements in an environmental chamber in order to better disentangle the responses of the BVOC emissions to driving factors that co-occur in field conditions and to determine the influence of single abiotic stressors on BVOC emissions. Next to a general presentation, some preliminary results of the project will be shown. [less ▲]

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See detailImproving energy partitioning and the nighttime energy balance by implementation of a multi-layer energy budget in ORCHIDEE-CAN
Chen, Yiying; Ryder, James; Naudts, Kim et al

in Geophysical Research Abstracts (2015, April), 17

Canopy structure is one of the most important vegetation characteristics for land-atmosphere interactions as it determines the energy and scalar exchanges between land surface and overlay air mass. In ... [more ▼]

Canopy structure is one of the most important vegetation characteristics for land-atmosphere interactions as it determines the energy and scalar exchanges between land surface and overlay air mass. In this study we evaluated the performance of a newly developed multi-layer energy budget (Ryder et al., 2014) in a land surface model, ORCHIDEE-CAN (Naudts et al., 2014), which simulates canopy structure and can be coupled to an atmospheric model using an implicit procedure. Furthermore, a vertical discrete drag parametrization scheme was also incorporated into this model, in order to obtain a better description of the sub-canopy wind profile simulation. Site level datasets, including the top-of-the-canopy and sub-canopy observations made available from eight flux observation sites, were collected in order to conduct this evaluation. The geo-location of the collected observation sites crossed climate zones from temperate to boreal and the vegetation types included deciduous, evergreen broad leaved and evergreen needle leaved forest with maximum LAI ranging from 2.1 to 7.0. First, we used long-term top-of-the-canopy measurements to analyze the performance of the current one-layer energy budget in ORCHIDEE-CAN. Three major processes were identified for improvement through the implementation of a multi-layer energy budget: 1) night time radiation balance, 2) energy partitioning during winter and 3) prediction of the ground heat flux. Short-term sub-canopy observations were used to calibrate the parameters in sub-canopy radiation, turbulence and resistances modules with an automatic tuning process following the maximum gradient of the user-defined objective function. The multi-layer model is able to capture the dynamic of sub-canopy turbulence, temperature and energy fluxes with imposed LAI profile and optimized parameter set at a site level calibration. The simulation result shows the improvement both on the nighttime energy balance and energy partitioning during winter and presents a better Taylor skill score, compared to the result from single layer simulation. The importance of using the multi-layer energy budget in a land surface model for coupling to the atmospheric model will also be discussed in this presentation. [less ▲]

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See detailModelling carbon fluxes of forest and grassland ecosystems in Western Europe using the CARAIB dynamic vegetation model: evaluation against eddy covariance data.
Henrot, Alexandra-Jane ULg; François, Louis ULg; Dury, Marie ULg et al

in Geophysical Research Abstracts (2015, April), 17

Eddy covariance measurements are an essential resource to understand how ecosystem carbon fluxes react in response to climate change, and to help to evaluate and validate the performance of land surface ... [more ▼]

Eddy covariance measurements are an essential resource to understand how ecosystem carbon fluxes react in response to climate change, and to help to evaluate and validate the performance of land surface and vegetation models at regional and global scale. In the framework of the MASC project (« Modelling and Assessing Surface Change impacts on Belgian and Western European climate »), vegetation dynamics and carbon fluxes of forest and grassland ecosystems simulated by the CARAIB dynamic vegetation model (Dury et al., iForest - Biogeosciences and Forestry, 4:82-99, 2011) are evaluated and validated by comparison of the model predictions with eddy covariance data. Here carbon fluxes (e.g. net ecosystem exchange (NEE), gross primary productivity (GPP), and ecosystem respiration (RECO)) and evapotranspiration (ET) simulated with the CARAIB model are compared with the fluxes measured at several eddy covariance flux tower sites in Belgium and Western Europe, chosen from the FLUXNET global network (http://fluxnet.ornl.gov/). CARAIB is forced either with surface atmospheric variables derived from the global CRU climatology, or with in situ meteorological data. Several tree (e.g. Pinus sylvestris, Fagus sylvatica, Picea abies) and grass species (e.g. Poaceae, Asteraceae) are simulated, depending on the species encountered on the studied sites. The aim of our work is to assess the model ability to reproduce the daily, seasonal and interannual variablility of carbon fluxes and the carbon dynamics of forest and grassland ecosystems in Belgium and Western Europe. [less ▲]

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See detailBiogenic Volatile Organic Compound (BVOC) emissions from agricultural crop species: is guttation a possible source for methanol emissions following light/dark transition?
Mozaffar, Ahsan ULg; Amelynck, Crist; Bachy, Aurélie ULg et al

in Geophysical Research Abstracts (2015, April), 17(EGU2015-2110-1),

In the framework of the CROSTVOC (CROp STress VOC) project, the exchange of biogenic volatile organic compounds (BVOCs) between two important agricultural crop species, maize and winter wheat, and the ... [more ▼]

In the framework of the CROSTVOC (CROp STress VOC) project, the exchange of biogenic volatile organic compounds (BVOCs) between two important agricultural crop species, maize and winter wheat, and the atmosphere has recently been measured during an entire growing season by using the eddy covariance technique. Because of the co-variation of BVOC emission drivers in field conditions, laboratory studies were initiated in an environmental chamber in order to disentangle the responses of the emissions to variations of the individual environmental parameters (such as PPFD and temperature) and to diverse abiotic stress factors. Young plants were enclosed in transparent all-Teflon dynamic enclosures (cuvettes) through which BVOC-free and RH-controlled air was sent. BVOC enriched air was subsequently sampled from the plant cuvettes and an empty cuvette (background) and analyzed for BVOCs in a high sensitivity Proton-Transfer Reaction Mass Spectrometer (hs-PTR-MS) and for CO2 in a LI-7000 non-dispersive IR gas analyzer. Emissions were monitored at constant temperature (25 °C) and at a stepwise varying PPFD pattern (0-650 µmol m-2 s-1). For maize plants, sudden light/dark transitions at the end of the photoperiod were accompanied by prompt and considerable increases in methanol (m/z 33) and water vapor (m/z 39) emissions. Moreover, guttation droplets appeared on the sides and the tips of the leaves within a few minutes after light/dark transition. Therefore the assumption has been raised that methanol is also coming out with guttation fluid from the leaves. Consequently, guttation fluid was collected from young maize and wheat plants, injected in an empty enclosure and sampled by PTR-MS. Methanol and a large number of other compounds were observed from guttation fluid. Recent studies have shown that guttation from agricultural crops frequently occurs in field conditions. Further research is required to find out the source strength of methanol emissions by this guttation phenomenon in real environmental conditions. [less ▲]

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See detailHow snow affects air-sea ice CO2 fluxes ?
Delille, Bruno ULg; Kotovitch, Marie ULg; Van Der Linden, Fanny ULg et al

Poster (2015, March)

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See detailNitrous oxide flux measurement with a closed chamber system : data treatment
Regaert, Donat ULg; Moureaux, Christine ULg; Heinesch, Bernard ULg et al

Poster (2015, January 30)

Nitrous oxide flux estimation from concentration measurements with a closed chamber system. Statistical data treatment to sort between relevant/irrelevant fluxes.

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See detailHow snow affects air-sea ice CO2 fluxes
Delille, Bruno ULg; Kotovitch, Marie ULg; Van Der Linden, Fanny ULg et al

Poster (2014, October)

Sea ice is a significant contributor to the sink of atmospheric CO2 by polar oceans. Physical and biogeochemical sea ice processes affect partial pressure of CO2 within sea ice, that in turn controls the ... [more ▼]

Sea ice is a significant contributor to the sink of atmospheric CO2 by polar oceans. Physical and biogeochemical sea ice processes affect partial pressure of CO2 within sea ice, that in turn controls the way and magnitude of air-sea ice CO2 fluxes. Snow cover appears to affect the magnitude of the fluxes. In order to understand the role of snow, we compared chamber and micrometeorological measurements of air-ice CO2 fluxes over snow covered and uncovered sea ice (land fast and pack ice) in both arctic and antarctic. We observed significant differences between fluxes over uncovered and covered sea ice. In addition chamber and micrometeorological measurement show different patterns that are partially due to snow cover. By gathering these observations, we observed at least three effects of snow on air-ice CO2 fluxes. Snow appears to (i) act as transient CO2 reservoir (ii) affect thermal properties of the ice surface (iii) control gas transfer depending on snow structure (superimposed ice, slush). [less ▲]

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See detailAre agricultural ecosystems important BVOC « exchangers »? Evidences from 2 measurement years on croplands at Lonzée Terrestrial Observatory (Belgium)
Bachy, Aurélie ULg; Aubinet, Marc ULg; Schoon, Niels et al

Poster (2014, September 23)

For the last decades, agricultural ecosystems have been a key biome for diverse socio-economical, environmental and climatic issues. And one of these climatic issues is just BVOC (Biogenic Volatile ... [more ▼]

For the last decades, agricultural ecosystems have been a key biome for diverse socio-economical, environmental and climatic issues. And one of these climatic issues is just BVOC (Biogenic Volatile Organic Compounds) emission from terrestrial ecosystems. Indeed, those compounds which are mostly emitted by plants play a great role in the atmospheric chemistry, thereby influencing the Earth surface radiative budget and the tropospheric air quality. However, so far, very few is known about BVOC exchange by crops, implying that huge uncertainties remain about qualifying, quantifying and determining sources/sinks and driving mechanisms of BVOC exchanges between croplands ecosystems and the atmosphere. We present here the first long term BVOC fluxes measurement study conducted on maize (2012) and winter wheat (2013), respectively the second and first most important worldwide crops (FAOSTAT). BVOC exchange was measured using the disjunct by mass scanning eddy covariance technique (+ PTR-MS, Ionicon) at the Lonzée Terrestrial Observatory (ICOS site) in Belgium. Main results are: (i) crops emit mainly methanol; (ii) BVOC emission from studied crops is lower than in literature, suggesting that agricultural ecosystems are poor BVOC exchangers; (iii) soil is a significant BVOC source. [less ▲]

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See detailAre agricultural ecosystems important BVOC « exchangers »? Evidences from 2 measurement years on croplands at Lonzée (Belgium)
Bachy, Aurélie ULg; Aubinet, Marc ULg; Schoon, Niels et al

Poster (2014, July 01)

For the last decades, agricultural ecosystems have been a key biome for diverse socio-economical, environmental and climatic issues. And one of these climatic issues is just BVOC (Biogenic Volatile ... [more ▼]

For the last decades, agricultural ecosystems have been a key biome for diverse socio-economical, environmental and climatic issues. And one of these climatic issues is just BVOC (Biogenic Volatile Organic Compounds) emission from terrestrial ecosystems. Indeed, those compounds which are mostly emitted by plants play a great role in the atmospheric chemistry, thereby influencing the Earth surface radiative budget and the tropospheric air quality. However, so far, very few is known about BVOC exchange by crops, implying that huge uncertainties remain about qualifying, quantifying and determining sources/sinks and driving mechanisms of BVOC exchanges between croplands ecosystems and the atmosphere. We present here the first long term BVOC fluxes measurement study conducted on maize (2012) and winter wheat (2013), respectively the second and first most important worldwide crops (FAOSTAT). BVOC exchange was measured using the disjunct by mass scanning eddy covariance technique (+ PTR-MS, Ionicon) at the Lonzée Terrestrial Observatory (ICOS site) in Belgium. Main results are: (i) crops emit mainly methanol; (ii) BVOC fluxes from studied crops is lower than in literature, suggesting that agricultural ecosystems are poor BVOC exchangers; (iii) soil is a significant BVOC source. [less ▲]

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See detailYear Round survey of Ocean-Sea Ice-Air Exchanges – the YROSIAE survey
Delille, Bruno ULg; Haskell, T.; Champenois, Willy ULg et al

Conference (2014, March)

YROSIAE survey aimed to carry out a year-round 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 ... [more ▼]

YROSIAE survey aimed to carry out a year-round 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. Ice cores, sea water, brines and exported material were collected at regular intervals about 1 km off cape Evans from November 2011 to December 2011 and from September 2012 to December 2012 in trace-metal clean conditions. Samples are processed to characterize both the vertical distribution and temporal changes of climate gases (CO2, DMS, CH4, N2O), CO2-related parameters (dissolved inorganic carbon, total alkalinity and CaCO3 amount), physical parameters (salinity, temperature, texture, 18O), biogeochemical parameters (macro-nutrients, particulate and dissolved organic carbon, δ13C, δ30Si and δ15N, micro-nutrients - including iron) and biological parameters ( chlorophyll a, primary production within sea ice derived from O2:Ar and O2:N ratios, autotrophic species determination, bacterial cell counts a.s.o.). In addition, we deployed a micro-meterological tower and automatic chambers to measure air-ice CO2 fluxes. Continuous measurements of ice temperature and ice accretion or melting, both at the ice-ocean and the ice-atmosphere interfaces were provided by an “Ice-T” ice mass balance buoy. Sediment traps collected particles below the ice between 10 and 70 m, while dust collectors provided a record of a full suite of trace metal and dust at different levels above the ground. We will present the aims, overall approach and sampling strategy of the YROSIAE survey. In addition we will also discuss CO2 dynamics within the ice and present temporal air-ice CO2 fluxes over the year. We will provide a first budget of air-ice CO2 fluxes during ice growth for Antarctica sea ice and discuss the impact of the snow cover on air-ice CO2 fluxes. [less ▲]

Detailed reference viewed: 107 (9 ULg)