References of "Delille, Bruno"      in Complete repository Arts & humanities   Archaeology   Art & art history   Classical & oriental studies   History   Languages & linguistics   Literature   Performing arts   Philosophy & ethics   Religion & theology   Multidisciplinary, general & others Business & economic sciences   Accounting & auditing   Production, distribution & supply chain management   Finance   General management & organizational theory   Human resources management   Management information systems   Marketing   Strategy & innovation   Quantitative methods in economics & management   General economics & history of economic thought   International economics   Macroeconomics & monetary economics   Microeconomics   Economic systems & public economics   Social economics   Special economic topics (health, labor, transportation…)   Multidisciplinary, general & others Engineering, computing & technology   Aerospace & aeronautics engineering   Architecture   Chemical engineering   Civil engineering   Computer science   Electrical & electronics engineering   Energy   Geological, petroleum & mining engineering   Materials science & engineering   Mechanical engineering   Multidisciplinary, general & others Human health sciences   Alternative medicine   Anesthesia & intensive care   Cardiovascular & respiratory systems   Dentistry & oral medicine   Dermatology   Endocrinology, metabolism & nutrition   Forensic medicine   Gastroenterology & hepatology   General & internal medicine   Geriatrics   Hematology   Immunology & infectious disease   Laboratory medicine & medical technology   Neurology   Oncology   Ophthalmology   Orthopedics, rehabilitation & sports medicine   Otolaryngology   Pediatrics   Pharmacy, pharmacology & toxicology   Psychiatry   Public health, health care sciences & services   Radiology, nuclear medicine & imaging   Reproductive medicine (gynecology, andrology, obstetrics)   Rheumatology   Surgery   Urology & nephrology   Multidisciplinary, general & others Law, criminology & political science   Civil law   Criminal law & procedure   Criminology   Economic & commercial law   European & international law   Judicial law   Metalaw, Roman law, history of law & comparative law   Political science, public administration & international relations   Public law   Social law   Tax law   Multidisciplinary, general & others Life sciences   Agriculture & agronomy   Anatomy (cytology, histology, embryology...) & physiology   Animal production & animal husbandry   Aquatic sciences & oceanology   Biochemistry, biophysics & molecular biology   Biotechnology   Entomology & pest control   Environmental sciences & ecology   Food science   Genetics & genetic processes   Microbiology   Phytobiology (plant sciences, forestry, mycology...)   Veterinary medicine & animal health   Zoology   Multidisciplinary, general & others Physical, chemical, mathematical & earth Sciences   Chemistry   Earth sciences & physical geography   Mathematics   Physics   Space science, astronomy & astrophysics   Multidisciplinary, general & others Social & behavioral sciences, psychology   Animal psychology, ethology & psychobiology   Anthropology   Communication & mass media   Education & instruction   Human geography & demography   Library & information sciences   Neurosciences & behavior   Regional & inter-regional studies   Social work & social policy   Sociology & social sciences   Social, industrial & organizational psychology   Theoretical & cognitive psychology   Treatment & clinical psychology   Multidisciplinary, general & others     Showing results 61 to 80 of 286     1 2 3 4 5 6 7 8 9     Factors driving pCO2 dynamics in sea ice during a large-scale ice tank experimentZhou, Jiayun ; Delille, Bruno ; Tison, J.-L. et alConference (2014, March)According to previous studies, pCO2 fluxes measured over Arctic sea ice are higher than those measured over Antarctic sea ice. We hypothesized that this was due to enhanced respiration in Arctic sea ice ... [more ▼]According to previous studies, pCO2 fluxes measured over Arctic sea ice are higher than those measured over Antarctic sea ice. We hypothesized that this was due to enhanced respiration in Arctic sea ice, as a consequence of higher riverine inputs of dissolved organic carbon (DOC) into Arctic seawater. We tested this hypothesis during the Interice V experiment at the HSVA (Hamburg) environmental test basin facility. We reproduced the growth and decay cycle of sea ice in replicate mesocosms (1 m3) filled with North Sea water (NSW series), and compared these with another series of mesocosms to which humic-rich river water had been added (10%) to increase the DOC concentration (R series). Primary producers were excluded from the experiment. The evolution of the temperature, salinity, DOC, pCO2 and bacterial biomass and production were measured in ice sampled at regular intervals throughout the experiment, as well as in the under-ice water. In addition, ice-air pCO2 fluxes were continuously monitored over both NSW and R mesocosms. pCO2 values in ice were higher in the R ice than in the NSW ice. This is attributed to the DOC content and bacterial respiration, rather than to the ice physical properties (i.e., ice permeability constrained by the ice temperature and salinity). Indeed, R ice had higher DOC content and bacterial production than the NSW ice while both showed similar physical properties. The evolution of the ice-air pCO2 fluxes was consistent with the evolution of pCO2 in ice. The fluxes were, as expected, positive (from sea ice to the atmosphere) during ice growth and negative (from the atmosphere to the ice) during ice melt. [less ▲]Detailed reference viewed: 95 (4 ULiège) Biological and physical controls on DMS,P dynamics in ice-shelf-influenced fast iceCarnat, G.; Zhou, Jiayun ; Papakyriakou, T. et alConference (2014, March)Dimethylsulfide (DMS) is a volatile sulphur compound produced by the degradation of dimethylsulphoniopropionate (DMSP), a metabolite synthesized by microalgae as i.a. cryoprotectant and osmoregulator. It ... [more ▼]Dimethylsulfide (DMS) is a volatile sulphur compound produced by the degradation of dimethylsulphoniopropionate (DMSP), a metabolite synthesized by microalgae as i.a. cryoprotectant and osmoregulator. It is also an important climate-active gas, being the primary source of marine-derived sulphate aerosols which play an important role in the earth-atmosphere radiation balance. In the last two decades, there has been an increasing interest in the role of the marine cryosphere in the DMS,P cycle, motivated by repeated observations of very high DMS,P concentrations in sea ice. However, our understanding of the factors driving the spatiotemporal variations of these high concentrations, and hence the fate of the sea ice DMS pool, remains limited. To date, studies have essentially focused on biotic factors, attributing the high DMS,P concentrations to the high biomass of the sympagic communities, and to their strong physiological response to the low temperature and high salinity stresses of the brine habitat. We present here an approach integrating both biotic and abiotic factors, as we investigate the influence of sea ice growth processes and brine dynamics on the DMS,P cycle. We focus on a fast ice site (Cape Evans, McMurdo Sound, Antarctica) under the influence of ice-shelf waters, and provide measurements covering a full cycle of ice growth. We show a good correspondence between isolated maxima of DMS,P in interior ice and the occurrence of platelet crystals in the ice texture. We develop the idea that platelet ice formation in May strongly modifies the production of DMS,P by (1) favoring the incorporation of strong DMSP producers and by (2) exposing these producers to stronger environmental stresses. We then show the influence of the development and decline of a strong diatom bloom from October to November on bottom ice DMS,P concentrations. Finally, we show that the increase in brine volume fraction (permeability) on warming in early December triggers (1) an important release of DMS to the ocean through brine convection, and (2) a vertical redistribution of DMSP across the ice. [less ▲]Detailed reference viewed: 108 (3 ULiège) Using stable isotopes to unravel the role of sea-ice in the methane cycleSapart, C.J.; Zhou, Jiayun ; Niemann, T et alPoster (2014, March)Methane (CH4) plays an important role in the Earth’s climate system. The atmospheric CH4 concentration has increased in concert with the industrialization, but since the mid 80’s the CH4 growth rate ... [more ▼]Methane (CH4) plays an important role in the Earth’s climate system. The atmospheric CH4 concentration has increased in concert with the industrialization, but since the mid 80’s the CH4 growth rate decreased to reach a near-zero level in 2000 and started to increase again from 2007 on. However, the underlying variations in sources and/or sinks that cause these variations are to date not well understood. To predict future climate, it is essential to unravel the processes controlling the CH4 cycle, especially in the Arctic regions, which are highly vulnerable to climate change and contain large CH4 reservoirs. Recently, an unexpected CH4 excess has been reported above Arctic sea-ice showing that sea-ice might play a significant role in the CH4 cycle. Nonetheless, the nature of the process leading to CH4 production in or nearby sea-ice has not yet been identified. We applied a new multi-proxy approach merging atmospheric chemistry, glaciology and biogeochemistry to understand and quantify the processes responsible for the CH4 excess above sea-ice. We performed CH4 isotope (13C and D) analyses on sea-ice samples, as well as microbial (lipid biomarkers) and geochemical measurements, to determine the possible pathways involved in CH4 production and removal in or nearby sea-ice. We will present results from sea-ice samples drilled above the shallow-shelf in Barrow (Alaska) from January to June 2009 as well as above deep Southern Ocean locations in 2013. Those results allow investigating the seasonality and spatial variability in methane formation and removal pathways associated to the methane enclosed in sea-ice. [less ▲]Detailed reference viewed: 113 (1 ULiège) Dimethyl sulfide and dimethylsulfoniopropionate profiles in sea ice during winter in the Weddell SeaUhlig, C.; Tison, J.-L.; Rintala, J. et alConference (2014, March)This study presents profiles of the organic sulphur components dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) in sea ice cores collected during the AWECS (Antarctic Winter Ecosytem Climate ... [more ▼]This study presents profiles of the organic sulphur components dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) in sea ice cores collected during the AWECS (Antarctic Winter Ecosytem Climate Study) cruise on RV Polarstern (ANT29-6) in the Weddell Sea. DMS is a semi-volatile sulfur component and under discussion to be climate active, as its oxidation products might act as cloud condensation nuclei - thus cooling the atmosphere. It is produced by enzymatic cleavage of the precursor DMSP, which is synthesized by various types of phytoplankton and serves for example as compatible solute and cryoprotectant. Due to the physico-chemical conditions given, i.e. the high salinity and the icy matrix, sea ice as habitat favors production of high levels of DMSP by the inhabiting microalgae. DMSP and DMS are frequently found in high concentrations in sea ice during spring and summer. The aim of this study was to investigate DMS(P) levels in winter sea ice as data for the winter season is yet scarce, but is of importance for global budgeting. Preliminary results of our study show that DMS(P) production in sea ice in the Weddell Sea is also significant during winter. This stands in contrast to previous measurements in Arctic winter sea ice (CFL-IPY cruise in the Circumpolar Flaw Lead Polynya), where DMS(P) concentrations were very low. Possible explanations for the differences between DMS(P) levels in the Arctic and Antarctic might be the different snow cover and thus insulation, light regimes and also microbial community structure within the ice. DMS(P) levels were generally correlated with chlorophyll a concentrations, although the details are complex and seem to be influenced by species composition and species specific DMSP/Chla ratios. The DMS profiles mirrored the permeability of the sea ice following DMSP in the impermeable areas while showing losses to the ice surface and ice-water interface in the more permeable regions. Winter DMS(P) profiles are furthermore compared to data collected during the following spring cruise of RV Polarstern (ANT29-7) in the Weddell Sea. [less ▲]Detailed reference viewed: 76 (2 ULiège) Land-fast sea ice of McMurdo Sound as a source of bio-essential trace metals for primary productivity in the Ross Sea, AntarcticaSchoemann, V.; de Jong, J.T.M.; Tison, J.L. et alConference (2014, March)Iron (Fe) is an essential micronutrient. Its low abundance limits primary productivity in more than 30% of the oceans, including the Southern Ocean, and has a crucial impact on the biogeochemical cycles ... [more ▼]Iron (Fe) is an essential micronutrient. Its low abundance limits primary productivity in more than 30% of the oceans, including the Southern Ocean, and has a crucial impact on the biogeochemical cycles of carbon and other elements with ultimate influence on the Earth climate system. Other trace metals, like Mn, Zn, Co and Cu are also required for microorganisms cell metabolism and may be (co-) limiting. Previous data on dissolved and particulate Fe concentration data showed that Fe is 10-100 times more concentrated in the sea ice than in underlying seawater and that sea ice melt can deliver up to 70% of the daily Fe supply to the surface waters. According to budget estimates in East Antarctica and in the Weddell Sea, accumulated Fe would largely derive from the underlying seawater rather than from atmospheric inputs. Most of the available data of trace metals in the sea ice concern pack ice and Fe. Only very scarce data exist on land-fast ice and on other trace metal concentrations. In this presentation, the general objective is to assess the role of land-fast ice as a source of Fe and other bio-essential trace metals (e.g. Mn, Zn, Cu, Mo, Cd), its impact on primary productivity and on the biological pump. Samples of sea ice, brines and seawater as well as dusts samples have been collected during the land-based sampling program YROSIAE at Cape Evans (Scott Base, McMurdo Sound, Ross Sea, Antarctica) from Nov 2011 to Dec 2011 and from Aug 2012 to Dec 2012. Dissolved and particulate trace metals concentrations have been measured by a recently developed method, which combines multiple element isotope dilution with preconcentration using the Nobias Chelate PA1 resin and ICP-MS analysis. Concentrations of trace metals in snow collected during the present study are one to up to five orders of magnitude higher than the concentrations previously observed in snow from East Antarctica, showing a much stronger dust input of these metals in McMurdo Sound. When comparing the concentrations obtained in the under-ice seawater with those obtained in the snow at McMurdo Sound, concentrations of Fe, Al, Mn, Co are much lower, whereas concentrations of Cu, Zn and Pb are similar and the concentrations of Ni, Mo and Cd are higher. Inventories of these trace metals in the land-fast sea ice give insights on its role as a source of bio-essential trace metal for the fuelling of the seasonal Ross Sea bloom. Other sources of these trace metals will be addressed and compared. [less ▲]Detailed reference viewed: 173 (7 ULiège) Modelling argon dynamics in first-year sea iceMoreau, S.; Vancoppenolle, M; Zhou, Jiayun et alin Ocean Modelling (2014), 73Abstract: Focusing on physical processes, we aim at constraining the dynamics of argon (Ar), a biogeochemically inert gas, within first year sea ice, using observation data and a one-dimensional halo ... [more ▼]Abstract: Focusing on physical processes, we aim at constraining the dynamics of argon (Ar), a biogeochemically inert gas, within first year sea ice, using observation data and a one-dimensional halo-thermodynamic sea ice model, including parameterization of gas physics. The incorporation and transport of dissolved Ar within sea ice and its rejection via gas-enriched brine drainage to the ocean, are modeled following fluid transport equations through sea ice. Gas bubbles nucleate within sea ice when Ar is above saturation and when the total partial pressure of all three major atmospheric gases (N2, O2 and Ar) is above the brine hydrostatic pressure. The uplift of gas bubbles due to buoyancy is allowed when the brine network is connected with a brine volume above a given threshold. Ice-atmosphere Ar fluxes are formulated as a diffusive process proportional to the differential partial pressure of Ar between brine inclusions and the atmosphere. Two simulations corresponding to two case studies that took place at Point Barrow (Alaska, 2009) and during an ice-tank experiment (INTERICE IV, Hamburg, Germany, 2009) are presented. Basal entrapment and vertical transport due to brine motion enable a qualitatively sound representation of the vertical profile of the total Ar (i.e. the Ar dissolved in brine inclusions and contained in gas bubbles; TAr). Sensitivity analyses suggest that gas bubble nucleation and rise are of most importance to describe gas dynamics within sea ice. Ice-atmosphere Ar fluxes and the associated parameters do not drastically change the simulated TAr. Ar dynamics are dominated by uptake, transport by brine dynamics and bubble nucleation in winter and early spring; and by an intense and rapid release of gas bubbles to the atmosphere in spring. Important physical processes driving gas dynamics in sea ice are identified, pointing to the need for further field and experimental studies. [less ▲]Detailed reference viewed: 54 (5 ULiège) Physical and biological controls on DMS,P dynamics in ice-shelf influenced fast ice during a winter-spring and a spring-summer transitionsCarnat, G.; Zhou, Jiayun ; Papakyriakou, T. et alin Journal of Geophysical Research. Oceans (2014), 119We report the seasonal and vertical variations of dimethylsulphide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) in fast ice at Cape Evans, McMurdo Sound (Antarctica) during the spring-summer ... [more ▼]We report the seasonal and vertical variations of dimethylsulphide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) in fast ice at Cape Evans, McMurdo Sound (Antarctica) during the spring-summer transition in 2011 and winter-spring transition in 2012. We compare the variations of DMS,P observed to the seasonal evolution of the ice algal biomass and of the physical properties of the ice cover, with emphasis on the ice texture and brine dynamics. Isolated DMS and DMSP maxima were found during both seasonal episodes in interior ice and corresponded to the occurrence of platelet crystals in the ice texture. We show that platelet crystals formation corresponded in time and depth to the incorporation of dinoflagellates (strong DMSP producers) in the ice cover. We also show that platelet crystals could modify the environmental stresses on algal cells and perturb the vertical redistribution of DMS,P concentrations. We show that during the winter-spring transition in 2012, the DMS,P profiles were strongly influenced by the development and decline of a diatom dominated bloom in the bottom ice, with DMSP variations remarkably following chl a variations. During the spring-summer transition in 2011, the increase in brine volume fraction (influencing ice permeability) on warming was shown to trigger (1) an important release of DMS to the under-ice water through brine convection (2) a vertical redistribution of DMSP across the ice [less ▲]Detailed reference viewed: 35 (3 ULiège) Southern Ocean CO2 sink: The contribution of the sea iceDelille, Bruno ; Vancoppenolle, M; Geilfus, N.-X. et alin Journal of Geophysical Research. Oceans (2014), 119We report first direct measurements of the partial pressure of CO2 (pCO2) within Antarctic pack sea ice brines and related CO2 fluxes across the air-ice interface. From late winter to summer, brines ... [more ▼]We report first direct measurements of the partial pressure of CO2 (pCO2) within Antarctic pack sea ice brines and related CO2 fluxes across the air-ice interface. From late winter to summer, brines encased in the ice change from a CO2 large over-saturation, relative to the atmosphere, to a marked under-saturation while the underlying oceanic waters remains slightly oversaturated. The decrease from winter to summer of pCO2 in the brines is driven by dilution with melting ice, dissolution of carbonate minerals crystals and net primary production. As the ice warms, its permeability increases, allowing CO2 transfer at the air-sea ice interface. The sea ice changes from a transient source to a sink for atmospheric CO2. We upscale these observations to the whole Antarctic sea-icesea ice cover using the NEMO-LIM3 large-scale sea ice-ocean, and provide first estimates of spring and summer CO2 uptake from the atmosphere by Antarctic sea ice. Over the spring-summer period, the Antarctic sea-icesea ice cover is a net sink of atmospheric CO2 of 0.029 PgC, about 58% of the estimated annual uptake from the Southern Ocean. Sea ice then contributes significantly to the sink of CO2 of the Southern Ocean. [less ▲]Detailed reference viewed: 94 (16 ULiège) Sea ice pCO2 dynamics and air–ice CO2 fluxes during the Sea Ice Mass Balance in the Antarctic (SIMBA) experiment – Bellingshausen Sea, AntarcticaGeilfus, N.-X.; Tison, J.-L.; Ackley, S. F. et alin Cryosphere (The) (2014), 8(6), 2395--2407Temporal evolution of pCO2 profiles in sea ice in the Bellingshausen Sea, Antarctica, in October 2007 shows physical and thermodynamic processes controls theCO2 sys- tem in the ice. During the survey ... [more ▼]Temporal evolution of pCO2 profiles in sea ice in the Bellingshausen Sea, Antarctica, in October 2007 shows physical and thermodynamic processes controls theCO2 sys- tem in the ice. During the survey, cyclical warming and cool- ing strongly influenced the physical, chemical, and thermo- dynamic properties of the ice cover. Two sampling sites with contrasting characteristics of ice and snow thickness were sampled: one had little snow accumulation (from 8 to 25 cm) and larger temperature and salinity variations than the sec- ond site, where the snow cover was up to 38 cm thick and therefore better insulated the underlying sea ice. We show that each cooling/warming event was associated with an in- crease/decrease in the brine salinity, total alkalinity (TA), to- tal dissolved inorganic carbon (TCO2), and in situ brine and bulk ice CO2 partial pressures (pCO2). Thicker snow covers reduced the amplitude of these changes: snow cover influ- ences the sea ice carbonate system by modulating the temper- ature and therefore the salinity of the sea ice cover. Results indicate that pCO2 was undersaturated with respect to the at- mosphere both in the in situ bulk ice (from 10 to 193 µatm) and brine (from 65 to 293 µatm), causing the sea ice to act as a sink for atmospheric CO2 (up to 2.9mmolm−2 d−1), despite supersaturation of the underlying seawater (up to 462 µatm) [less ▲]Detailed reference viewed: 124 (3 ULiège) CO2 and CH4 in sea ice from a subarctic fjord under influence of riverine inputCrabeck, O.; Delille, Bruno ; Thomas, David et alin Biogeosciences (2014), 11(23), 6525--6538We present the CH4 concentration [CH4], the par- tial pressure of CO2 (pCO2) and the total gas content in bulk sea ice from subarctic, land-fast sea ice in the Kapisillit fjord, Greenland. Fjord systems ... [more ▼]We present the CH4 concentration [CH4], the par- tial pressure of CO2 (pCO2) and the total gas content in bulk sea ice from subarctic, land-fast sea ice in the Kapisillit fjord, Greenland. Fjord systems are characterized by freshwater runoff and riverine input and based on $\delta$18O data, we show that >30\% of the surface water originated from periodic river input during ice growth. This resulted in fresher sea-ice layers with higher gas content than is typical from marine sea ice. The bulk ice [CH4] ranged from 1.8 to 12.1 nmolL−1, which corresponds to a partial pressure ranging from 3 to 28ppmv. This is markedly higher than the average atmo- spheric methane content of 1.9ppmv. Evidently most of the trapped methane within the icewas contained inside bubbles, and only a minor portion was dissolved in the brines. The bulk ice pCO2 ranged from 60 to 330ppmv indicating that sea ice at temperatures above −4 ◦C is undersaturated com- pared to the atmosphere (390 ppmv). This study adds to the few existing studies of CH4 and CO2 in sea ice, and we con- clude that subarctic seawater can be a sink for atmospheric CO2, while being a net source of CH4. [less ▲]Detailed reference viewed: 96 (0 ULiège) First ‘in situ’ determination of gas transport coefficients (DO2, DAr and DN2 ) from bulk gas 2 concentration measurements (O2, N2, Ar) in natural sea iceCrabeck, O.; Delille, Bruno ; Rysgaard, S. et alin Journal of Geophysical Research. Oceans (2014), 119We report bulk gas concentrations of O2, N2 and Ar, as well as their transport coefficients, in natural landfast subarctic sea ice in southwest Greenland. The observed bulk ice gas composition was 27.5 ... [more ▼]We report bulk gas concentrations of O2, N2 and Ar, as well as their transport coefficients, in natural landfast subarctic sea ice in southwest Greenland. The observed bulk ice gas composition was 27.5% O2, 71.4% N2 and 1.09% Ar. Most previous studies suggest that convective transport is the main driver of gas displacement in sea ice and have neglected diffusion processes. According to our data, brines were stratified within the ice, so that no convective transport could occur within the brine system. Therefore, diffusive transport was the main driver of gas migration. By analysing the temporal evolution of an internal gas peak within the ice, we deduced the bulk gas transport coefficients for oxygen (DO2), argon (DAr) and nitrogen (DN222 ). The values fit to the few existing estimates from experimental work, and are close to the diffusivity values in water (10-5 cm2 s-124 ). We suggest that gas bubbles escaping from the brine to the atmosphere - as the ice gets more permeable during melt could be responsible for the previously reported high transport coefficients. These results underline that when there is no convective transport within the sea ice, the transport of gas by diffusion through the brines, either in the liquid or gaseous phases, is a major factor in controlling the ocean–atmosphere exchange. [less ▲]Detailed reference viewed: 18 (0 ULiège) Insights into oxygen transport and net community production in sea ice from oxygen, nitrogen and argon concentrationsZhou, Jiayun ; Delille, Bruno ; Brabant, F. et alin Biogeosciences (2014), 11We present the evolution of O2 standing stocks, saturation levels and concentrations in landfast sea ice, collected in Barrow (Alaska), from February to June 2009. The comparison of the standing stocks ... [more ▼]We present the evolution of O2 standing stocks, saturation levels and concentrations in landfast sea ice, collected in Barrow (Alaska), from February to June 2009. The comparison of the standing stocks and saturation levels of O2 against those of N2 and Ar suggests that the dynamic of O2 in sea ice strongly depends on physical processes (gas incorporation and subsequent transport). We then discuss on the use of O2 / Ar and O2 / N2 to correct for the physical contribution and to determine the biological contribution (NCP) to O2 supersaturations. We conclude that O2 / Ar suits better than O2 / N2, because O2 / N2 is more sensitive due to the relative abundance of O2, N2 and Ar, and less biased when gas bubble formation and gas diffusion are maximized. We further estimate the NCP in the impermeable layers during ice growth and in the permeable layers during ice decay. Our results indicate that NCP contributed to a~release of carbon to the atmosphere in the upper ice layers, but to an uptake of carbon at sea ice bottom. Overall, seawater (rather than the atmosphere) may be the main supplier of carbon for sea ice microorganisms. [less ▲]Detailed reference viewed: 42 (7 ULiège) Air-Sea Interactions of Natural Long-Lived Greenhouse Gases (CO2, N2O, CH4) in a Changing ClimateBakker, Dorothee C. E.; Bange, Hermann W.; Gruber, Nicolas et alin Ocean-Atmosphere Interactions of Gases and Particles (2014)Detailed reference viewed: 94 (7 ULiège) Transfer across the air-sea interfaceGarbe; Rutgersson, Anna; Boutin, Jacqueline et alin Liss, Peter; Johnson, Martin (Eds.) Ocean-Atmosphere Interactions of Gases and Particles (2014)The efficiency of transfer of gases and particles across the air-sea interface is controlled by several physical, biological and chemical processes in the atmosphere and water which are described here ... [more ▼]The efficiency of transfer of gases and particles across the air-sea interface is controlled by several physical, biological and chemical processes in the atmosphere and water which are described here (including waves, large- and small-scale turbulence, bubbles, sea spray, rain and surface films). For a deeper understanding of relevant transport mechanisms, several models have been developed, ranging from conceptual models to numerical models. Most frequently the transfer is described by various functional dependencies of the wind speed, but more detailed descriptions need additional information. The study of gas transfer mechanisms uses a variety of experimental methods ranging from laboratory studies to carbon budgets, mass balance methods, micrometeorological techniques and thermographic techniques. Different methods resolve the transfer at different scales of time and space; this is important to take into account when comparing different results. Air-sea transfer is relevant in a wide range of applications, for example, local and regional fluxes, global models, remote sensing and computations of global inventories. The sensitivity of global models to the description of transfer velocity is limited; it is however likely that the formulations are more important when the resolution increases and other processes in models are improved. For global flux estimates using inventories or remote sensing products the accuracy of the transfer formulation as well as the accuracy of the wind field is crucial. [less ▲]Detailed reference viewed: 49 (1 ULiège) Short-term variability in bacterial abundance, cell properties, and incorporation of leucine and thymidine in subarctic sea iceKaartokallio, H.; Søgaard, D.H.; Norman, L. et alin Aquatic Microbial Ecology (2013), 71Sea ice is a biome of immense size and provides a range of habitats for diverse microbial communities many of which are adapted to living at low temperatures and high salinities in brines. We measured ... [more ▼]Sea ice is a biome of immense size and provides a range of habitats for diverse microbial communities many of which are adapted to living at low temperatures and high salinities in brines. We measured simultaneous incorporation of thymidine (TdR) and leucine (Leu), bacterial cell abundance and cell population properties (by flow cytometry) in subarctic sea ice in SW Greenland. Short-term temporal variability was moderate, and steep environmental gradients, typical for sea ice, were the main drivers of the variability in bacterial cell properties and activity. Low nucleic acid (LNA) bacteria, previously linked to oligotrophic ecotypes in marine habitats, were more abundant in the upper ice layers, whereas High nucleic acid (HNA) bacteria dominated in lower ice, where organic carbon was in high concentrations. Leucine incorporation was saturated at micro molar concentrations, as known from freshwater and marine biofilm systems. Leu:TdR ratios were high (up to >300) in lowermost ice layers and when they are compared to published respiration measurements these results suggest non-specific leucine incorporation. There was evidence of polyhydroxyalkanoate (PHA) containing bacteria in the sea ice, shown by brightly fluorescing intracellular inclusions after Nile Blue A staining. High leucine saturating concentrations coupled with the occurrence of PHA producing organisms further highlight the similarity of sea ice internal habitats to biofilm-like systems rather than to open-water systems. [less ▲]Detailed reference viewed: 23 (0 ULiège) Role of sea ice in global biogeochemical cycles: Emerging views and challengesVancoppenolle, M; Meiners, K.M.; Michel, C. et alin Quaternary Science Reviews (2013), 79Observations from the last decade suggest an important role of sea ice in the global biogeochemical cycles, promoted by (i) active biological and chemical processes within the sea ice; (ii) fluid and gas ... [more ▼]Observations from the last decade suggest an important role of sea ice in the global biogeochemical cycles, promoted by (i) active biological and chemical processes within the sea ice; (ii) fluid and gas exchanges at the sea ice interface through an often permeable sea ice cover; and (iii) tight physical, biological and chemical interactions between the sea ice, the ocean and the atmosphere. Photosynthetic micro-organisms in sea ice thrive in liquid brine inclusions encased in a pure ice matrix, where they find suitable light and nutrient levels. They extend the production season, provide a winter and early spring food source, and contribute to organic carbon export to depth. Under-ice and ice edge phytoplankton blooms occur when ice retreats, favoured by increasing light, stratification, and by the release of material into the water column. In particular, the release of iron – highly concentrated in sea ice – could have large effects in the iron-limited Southern Ocean. The export of inorganic carbon transport by brine sinking below the mixed layer, calcium carbonate precipitation in sea ice, as well as active iceatmosphere carbon dioxide (CO2) fluxes, could play a central role in the marine carbon cycle. Sea ice processes could also significantly contribute to the sulphur cycle through the large production by ice algae of dimethylsulfoniopropionate (DMSP), the precursor of sulfate aerosols, which as cloud condensation nuclei have a potential cooling effect on the planet. Finally, the sea ice zone supports significant ocean-atmosphere methane (CH4) fluxes, while saline ice surfaces activate springtime atmospheric bromine chemistry, setting ground for tropospheric ozone depletion events observed near both poles. All these mechanisms are generally known, but neither precisely understood nor quantified at large scales. As polar regions are rapidly changing, understanding the large-scale polar marine biogeochemical processes and their future evolution is of high priority. Earth system models should in this context prove essential, but they currently represent sea ice as biologically and chemically inert. Paleoclimatic proxies are also relevant, in particular the sea ice proxies, inferring past sea ice conditions from glacial and marine sediment core records and providing analogs for future changes. Being highly constrained by marine biogeochemistry, sea ice proxies would not only contribute to but also benefit from a better understanding of polar marine biogeochemical cycles. [less ▲]Detailed reference viewed: 193 (6 ULiège) Traces and Tracers: Selected papers from the Joint Liège Colloquium on Ocean Dynamics - Bonus- GoodHope - Geotraces meetingGrégoire, Marilaure ; Anderson, Bob; Delille, Bruno et alBook published by Journal of Marine Systems, Elsevier Science, 106p (2013)The 43rd International Liege Colloquium on Ocean Dynamics (http://modb.oce.ulg.ac.be/colloquium/) gathered a hundred scientists from around the world to discuss new developments and insights related to ... [more ▼]The 43rd International Liege Colloquium on Ocean Dynamics (http://modb.oce.ulg.ac.be/colloquium/) gathered a hundred scientists from around the world to discuss new developments and insights related to tracers and proxies (from temperature and salinity to gases and isotopes) with a particular attention on the use of Trace Elements and Isotopes (TEI) as tracers. The colloquium was organized in connection with the Geotraces program (an ongoing international study of the global marine biogeochemical cycles of trace elements and their isotopes, http://www.geotraces.org/) and was the occasion to present the wealth of data collected during large oceanographic expeditions that occurred in connection with the International Polar year. In this framework, particular emphasis was given to the BONUS-GoodHope project, a multi-disciplinary oceanographic cruise that coupled full-depth ocean and atmosphere physical and biogeochemical observations, including trace metals and isotopes (Speich et al. 2013; Speich et al. 2008). [less ▲]Detailed reference viewed: 37 (9 ULiège) Biogenic silica recycling in sea ice inferred from Si-isotopes: constraints from Arctic winter first-year sea iceFripiat, François ; Tison, Jean-Louis; André, Luc et alin 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 ▲]Detailed reference viewed: 29 (5 ULiège) First estimates of the contribution of CaCO3 precipitation to the release of CO2 to the atmosphere during young sea ice growthGeilfus, Nicolas-Xavier ; Carnat, Gauthier; Dieckmann, G.S. et alin Journal of Geophysical Research. Oceans (2013), 118(1-12), 244-255We 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 ▲]Detailed reference viewed: 37 (1 ULiège) Investigations 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 et alin 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 ▲]Detailed reference viewed: 27 (1 ULiège)