References of "Moreau, S"
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See detailN2O production and cycling within Antarctic sea ice
Kotovitch, Marie ULiege; Tison, J.-L.; Fripiat, François ULiege et al

Poster (2017, July)

Nitrous oxide (N2O) is a potent greenhouse gas that has a lifetime of 114 years in the atmosphere and a global warming potential 300 time higher than that of CO2. However there are still large ... [more ▼]

Nitrous oxide (N2O) is a potent greenhouse gas that has a lifetime of 114 years in the atmosphere and a global warming potential 300 time higher than that of CO2. However there are still large uncertainties and gaps in the understanding of the N2O cycle in polar oceans and particularly associated to sea ice. Sources and sinks of N2O are therefore poorly quantified. To date, only one study by Randall et al. 2012 present N2O measurements in sea ice. They pointed out that sea ice formation and melt has the potential to generate sea-air or air-sea fluxes of N2O, respectively. The main processes (except the transport processes) involved in the N2O cycle within the aquatic environment are nitrification and denitrification. 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. Our recent studies in Antarctic land fast ice in McMurdo Sound, confirmed this suggestion, where N2O release to the atmosphere was estimated to reach 4µmol.m-2.yr-1. But this assessment is probably an underestimation 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. We will then address the new tools to measure the bulk concentration of N2O (dissolved and gaseous) in sea ice, and the production of N2O by sympagic microorganisms - what process is dominant and how much N2O is produced - based on the first time series of N2O measurement in sea ice. The determination of the isotopic composition of N2O using cavity enhanced laser absorption spectroscopy technique (Off-axis ICOS) will allow us to determine the origin of these processes. [less ▲]

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See detailBiogeochemical Impact of Snow Cover and Cyclonic Intrusions on the Winter Weddell Sea Ice Pack
Tison, J.-L.; Schwegmann, S.; Dieckmann, G. et al

in Journal of Geophysical Research. Oceans (2017), 122(12), 9548--9571

Sea ice is a dynamic biogeochemical reactor and a double interface actively interacting with both the atmosphere and the ocean. However, proper understanding of its annual impact on exchanges, and ... [more ▼]

Sea ice is a dynamic biogeochemical reactor and a double interface actively interacting with both the atmosphere and the ocean. However, proper understanding of its annual impact on exchanges, and therefore potentially on the climate, notably suffer from the paucity of autumnal and winter data sets. Here we present the results of physical and biogeochemical investigations on winter Antarctic pack ice in the Weddell Sea (R. V. Polarstern AWECS cruise, June–August 2013) which are compared with those from two similar studies conducted in the area in 1986 and 1992. The winter 2013 was characterized by a warm sea ice cover due to the combined effects of deep snow and frequent warm cyclones events penetrating southward from the open Southern Ocean. These conditions were favorable to high ice permeability and cyclic events of brine movements within the sea ice cover (brine tubes), favoring relatively high chlorophyll-a (Chl-a) concentrations. We discuss the timing of this algal activity showing that arguments can be presented in favor of continued activity during the winter due to the specific physical conditions. Large-scale sea ice model simulations also suggest a context of increasingly deep snow, warm ice, and large brine fractions across the three observational years, despite the fact that the model is forced with a snowfall climatology. This lends support to the claim that more severe Antarctic sea ice conditions, characterized by a longer ice season, thicker, and more concentrated ice are sufficient to increase the snow depth and, somehow counterintuitively, to warm the ice. [less ▲]

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See detailHighly productive, yet heterotrophic, and still pumping CO2 from the atmosphere: A land fast ice paradigm?
Delille, Bruno ULiege; Van der Linden, Fanny ULiege; Conte, L et al

Conference (2016, October 21)

The YROSIAE (Year Round survey of Ocean-Sea Ice-Air Exchanges) survey aimed to carry out a year-round survey of land-fast sea ice focusing on the study of sea ice physics and biogeochemistry. Ice cores ... [more ▼]

The YROSIAE (Year Round survey of Ocean-Sea Ice-Air Exchanges) survey aimed to carry out a year-round survey of land-fast sea ice focusing on the study of sea ice physics and biogeochemistry. Ice cores, sea water, brines material were collected at regular intervals about 1 km off cape Evans in McMurdo Sound, Antarctica, from November 2011 to December 2011 and from September 2012 to December 2012. Samples were processed to characterize both the vertical distribution and temporal changes of climate gases (CO2, DMS, CH4, N2O), CO2-related parameters (ice-air CO2 fluxes, dissolved inorganic carbon, total alkalinity and CaCO3 amount), physical parameters (salinity, temperature, and ice texture), biogeochemical parameters (macro-nutrients, particulate and dissolved organic carbon, δ13C, δ30Si and δ15N) and biological parameters (chlorophyll a, primary production within sea ice derived from O2:Ar and O2:N ratios…). Very high chlorophyll a abundance was observed at the bottom of the ice, a common feature of land fast ice in McMurdo Sound. During spring, chlorophyll a exhibited a significant increase suggesting high primary production. . However, at the same time, nutrients at the bottom of the ice increased significantly suggesting high remineralization and heterotrophy. In the middle of the ice column, evolution of dissolved inorganic carbon shown a succession of autotrophic and heterotrophic phases. However, the overall increase of DIC suggests that the ice interior was rather heterotroph. This was consistent with the increase in nutrients observed at the bottom of the ice. Such sea ice system should expel CO2. Yet, strong under saturation in CO2 in surface ice, and negative air-ice CO2 fluxes suggested that sea ice was taking up CO2 from the atmosphere. Meanwhile, measurements of N2O within the sea ice suggest that the ice was releasing N2O to the atmosphere as a result of high nitrification. On the whole land fast sea ice in McMurdo Sound appears as a puzzling ecosystem. It is able to support elevated growth of autotrophic organisms, but appears to be heterotrophic, yet pumping CO2 to the atmosphere but releasing other greenhouse gases. [less ▲]

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See detailFlexible Transparent Electrodes based on Silver Nanowire Networks: Nanoscale Characterisation, Electrical Percolation, and Integration into Devices
Sannicolo, T.; Lagrange, M.; Xian, S. et al

Conference (2016, September)

The most efficient and widely used transparent conducting material (TCM) is currently indium tin oxide (ITO). However the indium scarcity associated to the lack of flexibility of ITO as well as relatively ... [more ▼]

The most efficient and widely used transparent conducting material (TCM) is currently indium tin oxide (ITO). However the indium scarcity associated to the lack of flexibility of ITO as well as relatively high cost of fabrication has prompted the search for alternative low cost and flexible materials. Among emerging transparent electrodes (TEs), silver nanowire (AgNW) networks appear as a promising substitute to ITO since these percolating networks exhibit high flexibility and excellent optoelectronic properties [1], with sheet resistance of a few Ω/sq and optical transparency of 90%, fulfilling the requirements for many applications such as solar cells, OLED displays, transparent heaters, or radio-frequency (RF) antennas and transparent shielding [2]. In addition, the fabrication of these electrodes involves low-temperature process steps and upscaling methods, thus making them very appropriate for future use as TE for flexible devices. Our research is focused on the fundamental understanding of the physical phenomena taking place at the scales of both the network (macroscale) and the NW-to- NW junctions (nanoscale), and on the ability of AgNW networks to be integrated as transparent electrodes for flexible optoelectronic and RF devices. In-situ electrical measurements performed during optimisation process such as thermal annealing and/or chemical treatments provide useful information regarding the activation process of the junctions [3]. Besides, nano-characterisation techniques such as Transmission Electron Microscopy (TEM) and ultramicrotomy help visualizing the physical phenomena involved in the diffusion of silver atoms to create well-sintered junctions. At the network’s scale, our ability to distinguish the nanowires taking part in the electrical conduction (“electrical percolating pathways”) from the inactive nanowires is a critical issue for the applications. By combining experimental and simulation studies, a discrete activation process of efficient percolating pathways through the network was evidenced. In the case where the network density is close to the percolation threshold and when low voltage is applied, individual “illuminated” pathways can be detected through the network while new branches get activated as soon as the voltage is increased. Here we will present our results on the study of AgNW networks at the macro and nano scales described above and will correlate it with the overall performance/characteristics of the networks. We will also present results on the integration of optimized AgNW networks into functional devices. [1] D.P. Langley, G. Giusti, C. Mayousse, C. Celle, D. Bellet, J.-P. Simonato, Nanotechnology, 24, 452001, (2013). [2] C. Celle, C. Mayousse, E. Moreau, H. Basti, A. Carella and J.-P. Simonato, Nano Res. 5, 427, (2012). [3] M. Lagrange, D.P. Langley, G. Giusti, C. Jimenez, Y. Bréchet, D. Bellet, Nanoscale 7, 17410, (2015). [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 detailThe impact of dissolved organic carbon and bacterial respiration on pCO2 in experimental sea ice
Zhou, Jiayun; Kotovitch, Marie ULiege; Kaartokallio, H. et al

in Progress in Oceanography (2016), 141

Previous observations have shown that the partial pressure of carbon dioxide (pCO2) in sea ice brines is generally higher in Arctic sea ice compared to those from the Antarctic sea ice, especially in ... [more ▼]

Previous observations have shown that the partial pressure of carbon dioxide (pCO2) in sea ice brines is generally higher in Arctic sea ice compared to those from the Antarctic sea ice, especially in winter and early spring. We hypothesized that these differences result from the higher dissolved organic carbon (DOC) content in Arctic seawater: Higher concentrations of DOC in seawater would be reflected in a greater DOC incorporation into sea ice, enhancing bacterial respiration, which in turn would increase the pCO2 in the ice. To verify this hypothesis, we performed an experiment using two series of mesocosms: one was filled with seawater (SW) and the other one with seawater with an addition of filtered humic-rich river water (SWR). The addition of river water increased the DOC concentration of the water from a median of 142 µmol L-1 in SW to 249 µmol L-1 in SWR. Sea ice was grown in these mesocosms under the same physical conditions over 19 days. Microalgae and protists were absent, and only bacterial activity has been detected. We measured the DOC concentration, bacterial respiration, total alkalinity and pCO2 in sea ice and the underlying seawater, and we calculated the changes in dissolved inorganic carbon (DIC) in both media. We found that bacterial respiration in ice was higher in SWR: median bacterial respiration was 25 nmol C L-1 h-1 compared to 10 nmol C L-1 h-1 in SW. pCO2 in ice was also higher in SWR with a median of 430 ppm compared to 356 ppm in SW. However, the differences in pCO2 were larger within the ice interiors than at the surfaces or the bottom layers of the ice, where exchanges at the air-ice and ice-water interfaces might have reduced the differences. In addition, we used a model to simulate the differences of pCO2 and DIC based on bacterial respiration. The model simulations support the experimental findings and further suggest that bacterial growth efficiency in the ice might be 0.15-0.2. It is thus credible that the higher pCO2 in Arctic sea ice brines compared with those from the Antarctic sea ice were due to an elevated bacterial respiration, sustained by higher riverine DOC loads. These conclusions should hold for locations and time frames when bacterial activity is relatively dominant compared to algal activity, considering our experimental conditions. [less ▲]

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See detailAssessing the O2 budget under sea ice: An experimental and modelling approach
Moreau, S.; Kaartokallio, H.; Vancoppenolle, M. et al

in Elementa: Science of the Anthropocene (2015), 3(000080),

The objective of this study was to assess the O2 budget in the water under sea ice combining observations and modelling. Modelling was used to discriminate between physical processes, gas-specific ... [more ▼]

The objective of this study was to assess the O2 budget in the water under sea ice combining observations and modelling. Modelling was used to discriminate between physical processes, gas-specific transport (i.e., ice-atmosphere gas fluxes and gas bubble buoyancy) and bacterial respiration (BR) and to constrain bacterial growth efficiency (BGE). A module describing the changes of the under-ice water properties, due to brine rejection and temperature-dependent BR, was implemented in the one-dimensional halo-thermodynamic sea ice model LIM1D. Our results show that BR was the dominant biogeochemical driver of O2 concentration in the water under ice (in a system without primary producers), followed by gas specific transport. The model suggests that the actual contribution of BR and gas specific transport to the change in seawater O2 concentration was 37% during ice growth and 48% during melt. BGE in the water under sea ice, as retrieved from the simulated O2 budget, was found to be between 0.4 and 0.5, which is in line with published BGE values for cold marine waters. Given the importance of BR to seawater O2 in the present study, it can be assumed that bacteria contribute substantially to organic matter consumption and gas fluxes in ice-covered polar oceans. In addition, we propose a parameterization of polar marine bacterial respiration, based on the strong temperature dependence of bacterial respiration and the high growth efficiency observed here, for further biogeochemical ocean modelling applications, such as regional or large-scale Earth System models [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 ULiege; Zhou, Jiayun; Kotovitch, Marie ULiege 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 detailDetermination of air‐sea ice transfer coefficient for CO2: Significant contribution of gas bubble transport during sea ice growth
Kotovitch, Marie ULiege; Moreau, S.; Zhou, Jiayun et al

Poster (2015, September)

Air‐ice CO2 fluxes were measured continuously from the freezing of a young sea‐ice cover until its decay. Cooling seawater was as a sink for atmospheric CO2 but asthe ice crystalsformed,sea ice shifted to ... [more ▼]

Air‐ice CO2 fluxes were measured continuously from the freezing of a young sea‐ice cover until its decay. Cooling seawater was as a sink for atmospheric CO2 but asthe ice crystalsformed,sea ice shifted to a source releasing CO2 to the atmosphere throughout the whole ice growth. Atmospheric warming initiated the decay, re‐shifting sea‐ice to a CO2 sink. Combining these CO2 fluxes with the partial pressure of CO2 within sea ice, we determined gas transfer coefficients for CO2 at air‐ice interface for growth and decay. We hypothesize that this difference originates from the transport of gas bubbles during ice growth, while only diffusion occurs during ice melt. In parallel, we used a 1D biogeochemical model to mimic the observed CO2 fluxes. The formation of gas bubbles was crucial to reproduce fluxes during ice growth where gas bubbles may account for up to 92 % of the upward CO2 fluxes. [less ▲]

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See detailSea ice in the global biogeochemical cycles: How much do we care?
Vancoppenolle, M.; Moreau, S.; Bopp, L. et al

Conference (2015, September)

Large changes in the state and seasonality of sea ice are expected for this century in both hemispheres. The impact of these changes on marine biogeochemical cycles and ecosystems is difficult to predict ... [more ▼]

Large changes in the state and seasonality of sea ice are expected for this century in both hemispheres. The impact of these changes on marine biogeochemical cycles and ecosystems is difficult to predict. Will the polar oceans be more or less biologically productive? Will they take up more or less carbon? At this stage, the answers to these key questions are not obvious. Marine biogeochemical cycles in the sea ice zone are characterized by specific processes that have been unravelled over the last 20 years or so. They involve active biological and chemical processes within the sea ice, the modulation of heat and gas exchanges by the ice cover; and the impact of growing and melting sea ice on the water column stratification and vertical exchanges in the water. To understand how sea ice influences marine biogeochemical cycles, the sea ice biogeochemical community focuses on: (i) the synthesis of existing data and the interpretation of robust large-scale patterns; (ii) the introduction of new representations of sea ice processes into large-scale models of the Earth System and the study of their impact; (iii) the evaluation of existing observation methods and the development of new ones. In this talk, I will review and synthesize recent research activities in these lines of thought. [less ▲]

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

Conference (2015, May 16)

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. Carbonate chemistry, the consumption and release of CO2 by primary production and respiration, the precipitation and dissolution of ikaite (CaCO3•6H2O) and ice-air CO2 fluxes, are also included. The model is evaluated using observations from a 6-month field study at Point Barrow, Alaska and an ice-tank experiment. At Barrow, results show that the DIC budget is mainly driven by physical processes, wheras brine-air CO2 fluxes, ikaite formation, and net primary production, are secondary factors. In terms of ice-atmosphere CO 2 exchanges, sea ice is a net CO2 source and sink in winter and summer, respectively. The formulation of the ice-atmosphere CO2 flux impacts the simulated near-surface CO2 partial pressure (pCO2), but not the DIC budget. Because the simulated ice-atmosphere CO2 fluxes are limited by DIC stocks, and therefore < 2 mmol m-2 day-1, we argue that the observed much larger CO2 fluxes from eddy covariance retrievals cannot be explained by a sea ice direct source and must involve other processes or other sources of CO2. Finally, the simulations suggest that near surface TA/DIC ratios of 2, sometimes used as an indicator of calcification, would rather suggest outgassing. [less ▲]

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See detailThe role of sea ice in the carbon cycle of Polar Seas: 1D to 3D modelling
Moreau, S.; Vancoppenolle, M.; Delille, Bruno ULiege et al

Poster (2015, May)

Sea ice participates actively in the biogeochemical cycle of carbon of Polar Oceans, yet to which extent is not clear. We investigated the processes that govern sea ice carbon dy- namics in Polar Regions ... [more ▼]

Sea ice participates actively in the biogeochemical cycle of carbon of Polar Oceans, yet to which extent is not clear. We investigated the processes that govern sea ice carbon dy- namics in Polar Regions through 1D to 3D modelling developments. First, we constrained all major physical and biogeochemical processes with respect to CO2 dynamics (carbon- ate chemistry, biological activity, ikaite (CaCO3•6H2O) precipitation and dissolution and ocean-ice-air CO2 fluxes) in a one-dimensional sea ice model. According to our model, the CO2 budget is driven by the CO2 uptake during ice growth and release by brine drainage, whereas other processes such as brine-air CO2 fluxes, despite significant, are secondary. Subsequently, based on these preliminary conclusions, we evaluated the role of sea ice in the carbon dynamics of Polar Oceans by using an ocean-ice coupled Global Earth System Model. Carbon dynamics (e.g. ocean-atmosphere CO2 fluxes) are driven by the contribution of sea ice growth regions in the Arctic Ocean (mainly the Siberian coast) and sea ice melt regions in the Southern Ocean (off the coast of Antarctica). In addition, the production of deep waters is low in the Arctic Ocean but significant in the Southern Ocean. Therefore, sea ice only contributes to the deep water export of carbon in the Southern Ocean. The role of sea ice in the biogeochemical cycle of carbon is significant and its representation by Global Earth System Models should be improved. [less ▲]

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See detailThe role of sea ice in the carbon cycle of Polar Seas: 1D to 3D modelling
Moreau, S.; Vancoppenolle, M.; Delille, Bruno ULiege et al

Poster (2015, March)

Detailed reference viewed: 23 (5 ULiège)
See detailYear Round survey of Ocean-Sea Ice-Air Exchanges – the YROSIAE survey
Delille, Bruno ULiege; Haskell, T.; Champenois, Willy ULiege 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 ▲]

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See detailLand-fast sea ice of McMurdo Sound as a source of bio-essential trace metals for primary productivity in the Ross Sea, Antarctica
Schoemann, V.; de Jong, J.T.M.; Tison, J.L. et al

Conference (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 ▲]

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See detailModelling argon dynamics in first-year sea ice
Moreau, S.; Vancoppenolle, M; Zhou, Jiayun ULiege et al

in Ocean Modelling (2014), 73

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 ... [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 ▲]

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See detailRole of sea ice in global biogeochemical cycles: Emerging views and challenges
Vancoppenolle, M; Meiners, K.M.; Michel, C. et al

in Quaternary Science Reviews (2013), 79

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 ... [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 ▲]

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See detailModeling argon dynamics in first-year sea ice
Moreau, S.; Vancoppenolle, M.; Tison, J.-L. et al

Poster (2012, July)

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