References of "Delille, Bruno"
     in
Bookmark and Share    
See detailAn active bacterial community linked to high chl-a concentrations in Antarctic winter-pack ice and evidence for the development of an anaerobic sea-ice bacterial community
Eronen-Rasimus; Luhtanen, A.-M.; Rintala, J.-M. et al

Poster (2017, September)

Detailed reference viewed: 17 (1 ULiège)
Full Text
Peer Reviewed
See detailAn active bacterial community linked to high chl-a concentrations in Antarctic winter-pack ice and evidence for the development of an anaerobic sea-ice bacterial community
Eronen-Rasimus, Eeva; Luhtanen, Anne-Mari; Rintala, Janne-Markus et al

in ISME Journal (The) (2017), 1-11

Antarctic sea-ice bacterial community composition and dynamics in various developmental stages were investigated during the austral winter in 2013. Thick snow cover likely insulated the ice, leading to ... [more ▼]

Antarctic sea-ice bacterial community composition and dynamics in various developmental stages were investigated during the austral winter in 2013. Thick snow cover likely insulated the ice, leading to high (o4 μg l–1) chlorophyll-a (chl-a) concentrations and consequent bacterial production. Typical sea-ice bacterial genera, for example, Octadecabacter, Polaribacter and Glaciecola, often abundant in spring and summer during the sea-ice algal bloom, predominated in the communities. The variability in bacterial community composition in the different ice types was mainly explained by the chl-a concentrations, suggesting that as in spring and summer sea ice, the sea-ice bacteria and algae may also be coupled during the Antarctic winter. Coupling between the bacterial community and sea-ice algae was further supported by significant correlations between bacterial abundance and production with chl-a. In addition, sulphate-reducing bacteria (for example, Desulforhopalus) together with odour of H2S were observed in thick, apparently anoxic ice, suggesting that the development of the anaerobic bacterial community may occur in sea ice under suitable conditions. In all, the results show that bacterial community in Antarctic sea ice can stay active throughout the winter period and thus possible future warming of sea ice and consequent increase in bacterial production may lead to changes in bacteria-mediated processes in the Antarctic sea-ice zone. [less ▲]

Detailed reference viewed: 24 (3 ULiège)
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 ▲]

Detailed reference viewed: 17 (1 ULiège)
See detailWhere does the methane entrapped in Antarctic sea ice come from?
Jacques, C.; Sapart, Célia Julia ULiege; Carnat, G. et al

Poster (2017, July)

Methane (CH4) atmospheric concentrations have increased by a factor of 2.5 since the beginning of the Industrial Era, mainly because of anthropogenic activities. However, between 1999 and 2006, CH4 growth ... [more ▼]

Methane (CH4) atmospheric concentrations have increased by a factor of 2.5 since the beginning of the Industrial Era, mainly because of anthropogenic activities. However, between 1999 and 2006, CH4 growth rate declined to a near-zero level, suggesting that an equilibrium had been reached. But, from 2007 on, atmospheric concentrations underwent a renewed growth, implying major ongoing changes in the CH4 global budget (Nisbet et al., 2016). These changes challenge our understanding on the contribution of existing sources, and in particular natural sources. Sea ice can strongly affect emissions of CH4 from the ocean, but the precise mechanisms are not well understood. Sea ice has long been considered as an inert and impermeable barrier, but recent studies have highlighted the existence of gas fluxes at the atmosphere-sea ice and sea ice-seawater interfaces (Kort et al., 2012; He et al., 2013; Zhou et al., 2014; Sapart et al., 2016). However, these fluxes are to date poorly understood and quantified. To improve future climate projections, we aim to investigate the control exerted by sea ice on the CH4 atmospheric budget. To unravel the impacts of the Antarctic sea ice physical environment on biogeochemical cycles, the AWECS (Antarctic Winter Ecosystem Climate Study) expedition was conducted between the 8th of June and the 12th of August 2013 in the Weddell Sea. Such an expedition provides a rare opportunity to obtain insights on the behaviour of sea ice during winter. Ice cores specifically dedicated to the investigation of gas dynamics were collected at ten different stations. In order to determine CH4 formation and removal pathways in sea ice, we used concentration and stable isotope analysis, which can help to distinguish different processes. Here, we present and discuss our first results of the isotopic composition of CH4 (δ13C and δ D) on sea ice cores from the Weddell Sea and the Ross Ice Shelf. This new dataset will help to determine the origin of the CH4 entrapped in Antarctic sea ice and its potential impact on the current and future atmospheric CH4 budget. [less ▲]

Detailed reference viewed: 15 (1 ULiège)
See detailAntarctic sea ice trophic status
Van der Linden, Fanny ULiege; Moreau, Sébastien; Champenois, Willy ULiege et al

Poster (2017, July)

The sea ice ecosystem is characterized by steep gradients in temperature, salinity, light and nutrient availability. Despite these challenging environmental conditions, sea ice provides a dynamic habitat ... [more ▼]

The sea ice ecosystem is characterized by steep gradients in temperature, salinity, light and nutrient availability. Despite these challenging environmental conditions, sea ice provides a dynamic habitat for diverse communities of microorganisms. These communities include a wide variety of organisms from different taxonomic groups such as algae, bacteria, heterotrophic protists, fungi as well as viruses [Horner et al., 1992; Deming, 2010; Thomas and Dieckmann, 2010; Poulin et al., 2011]. In the frame of the YROSIAE project (Year-Round survey of Ocean-Sea-Ice-Atmosphere Exchanges), carried out at Cape Evans in McMurdo Sound (Antarctica) from Nov. 2011 to Dec. 2012, ice cores, seawater, and brine material were collected at regular time intervals. Physical properties (salinity, temperature, texture) and biogeochemical parameters (pCO2, dissolved inorganic carbon, total alkalinity, chlorophyll-a, macro-nutrients) were analysed. We will here particularly consider changes inused dissolved inorganic carbon (DIC) and chlorophyll-a (chl-a) , used as a proxiesy of net community production and autotrophic biomass, respectively. A high spatial and temporal variability in ice algal biomass and DIC evolution were observed. From spring, very high chl-a concentrations (>2400μg.L^(-1)) were observed at the bottom of the ice, a common feature of land fast ice in the McMurdo Sound. This suggests high primary production. However Strikingly, , at the same time, nutrients at the bottom of the ice increased significantly suggesting high heterotrophyremineralisation. In the middle of the ice column, evolution of DIC is was marked by a succession of autotrophic and heterotrophic phases. The overall increase of DIC suggests that the ice interior was rather heterotroph. Such sea ice system should expel CO2. Yet, strong under-saturation in CO2 and DIC depletion appeared at the ice surface, suggesting that sea ice was taking up CO2 from the atmosphere. 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 at the bottom, but still appears to be heterotrophicin parallel to high remineralization, while the top of the ice appears to be rather heterotrophic but stilland able to pump CO2 from the atmosphere. [less ▲]

Detailed reference viewed: 27 (5 ULiège)
Full Text
Peer Reviewed
See detailMacro-nutrient concentrations in Antarctic pack ice: Overall patterns and overlooked processes
Fripiat, François ULiege; Meiners, K.M.; Vancoppenolle, M. et al

in Elementa: Science of the Anthropocene (2017), 5(13),

Antarctic pack ice is inhabited by a diverse and active microbial community reliant on nutrients for growth. Seeking patterns and overlooked processes, we performed a large-scale compilation of macro ... [more ▼]

Antarctic pack ice is inhabited by a diverse and active microbial community reliant on nutrients for growth. Seeking patterns and overlooked processes, we performed a large-scale compilation of macro-nutrient data (hereafter termed nutrients) in Antarctic pack ice (306 ice-cores collected from 19 research cruises). Dissolved inorganic nitrogen and silicic acid concentrations change with time, as expected from a seasonally productive ecosystem. In winter, salinity-normalized nitrate and silicic acid concentrations (C*) in sea ice are close to seawater concentrations (Cw), indicating little or no biological activity. In spring, nitrate and silicic acid concentrations become partially depleted with respect to seawater (C* < Cw), commensurate with the seasonal build-up of ice microalgae promoted by increased insolation. Stronger and earlier nitrate than silicic acid consumption suggests that a significant fraction of the primary productivity in sea ice is sustained by flagellates. By both consuming and producing ammonium and nitrite, the microbial community maintains these nutrients at relatively low concentrations in spring. With the decrease in insolation beginning in late summer, dissolved inorganic nitrogen and silicic acid concentrations increase, indicating imbalance between their production (increasing or unchanged) and consumption (decreasing) in sea ice. Unlike the depleted concentrations of both nitrate and silicic acid from spring to summer, phosphate accumulates in sea ice (C* > Cw). The phosphate excess could be explained by a greater allocation to phosphorus-rich biomolecules during ice algal blooms coupled with convective loss of excess dissolved nitrogen, preferential remineralization of phosphorus, and/or phosphate adsorption onto metal-organic complexes. Ammonium also appears to be efficiently adsorbed onto organic matter, with likely consequences to nitrogen mobility and availability. This dataset supports the view that the sea ice microbial community is highly efficient at processing nutrients but with a dynamic quite different from that in oceanic surface waters calling for focused future investigations. [less ▲]

Detailed reference viewed: 27 (2 ULiège)
See detailN2O dynamics in sea ice, insights from a first time series and isotopic tools
Kotovitch, Marie ULiege; Tison, Jean-Louis; Fripiat, François et al

Conference (2017, March 25)

Nitrous oxide (N2O) is a potent greenhouse gases 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 gases 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 4 µmol.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 ▲]

Detailed reference viewed: 46 (6 ULiège)
Full Text
See detailGases in sea ice
Tison, J.-L.; Delille, Bruno ULiege; Papadimitriou, Stathys

in Thomas, D.N. (Ed.) Sea ice (third edition) (2017)

Detailed reference viewed: 12 (2 ULiège)
See detailNitrous oxide dynamic in sea ice
Kotovitch, Marie ULiege; Fripiat, François ULiege; Deman, Florian et al

Poster (2017)

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

Fluctuations in greenhouse gases (GHGs) concentration alter the energetic budget of the climate system. There is high confidence that natural systems related to snow, ice and frozen ground are affected. Nitrous oxide (N2O) is one of the potent GHG naturally present in the atmosphere, but witch has seen his concentration growing since industrial era. N2O has a lifetime in the atmosphere of 114 years and a global warming potential 300 time higher than that of CO2. Yet, there are still large uncertainties and gaps in the understanding of the cycle of this compound through the ocean and particularly in sea ice. Sources and sinks of N2O are therefore still poorly quantified. The main processes (except the transport processes) involved in the N2O cycle within the aquatic environment are nitrification and denitrification. To date, only one study by Randall et al. 2012 present N2O measurements in sea ice. Randall et al. pointed out that sea ice formation and melt has the potential to generate sea-air or air-sea fluxes of N2O, respectively. Study on ammonium oxidation and anaerobic bacterial cultures shows that N2O production can potentially occur in sea ice. Denitrification can act as a sink or a source of N2O. In strictly anaerobic conditions, N2O is removed by denitrification. However, denitrification can also occur in presence of O2 at trace level concentrations (<0.2 mg L-1), and in these conditions there is a large N2O production. Recent observations of significant nitrification in Antarctic sea ice shed a new light on nitrogen cycle within sea ice. It has been suggested that nitrification supplies up to 70% of nitrate assimilated within Antarctic spring sea ice. Corollary, production of N2O, a by-product of nitrification, can potentially be significant. This was recently confirmed in Antarctic land fast ice in McMurdo Sound, where N2O release to the atmosphere was estimated to 4 µmol.m-2.yr-1. This assessment is probably an underestimate since it only accounts for dissolved N2O while a significant amount of N2O is likely to occur in the gaseous form like N2, O2 and Ar. This poster address the issue related to the production of N2O within sympagic microorganisms. What process is dominant and how much N2O is produced? 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. It will be based on the relative isotope abundance values and site preference data in previous studies. [less ▲]

Detailed reference viewed: 29 (6 ULiège)
See detailSea ice: Source or sink of nitrous oxide?
Kotovitch, Marie ULiege; Fripiat, François ULiege; Moreau, Sebastien et al

Conference (2016, October 21)

Detailed reference viewed: 32 (6 ULiège)
See detailA time series study during spring transition in the fast ice at Davis station, Antarctica: preliminary resul
Deman, F.; Roukaerts, A.; Delille, Bruno ULiege et al

Conference (2016, October 21)

While representing less than 5% of the total ice cover around Antarctica, fast ice is nevertheless an important habitat with highest biomass and production occurring in the bottom (Archer et al., 1996 ... [more ▼]

While representing less than 5% of the total ice cover around Antarctica, fast ice is nevertheless an important habitat with highest biomass and production occurring in the bottom (Archer et al., 1996). Sea--‐ice algae are playing a key role in structuring the ecosystem, as they are an essential food source for krill. With the annual melting of the sea ice there is a strong release of nutrients and algae to the water, possibly fertilizing and/or seeding algae the underlying water column. A time series was sampled during the Austral spring of 2015 (Oct. 27th – Dec. 11th), in the vicinity of Davis station (68°35’ S, 77°58’ E, Prydz Bay, Antarctica). Fast ice, snow cover and underlying water column were sampled with focus on the nitrogen and carbon cycle and the pivotal role of sea--‐ice algae for higher tropic levels. Different parameters such as nutrients, particulate matter (PM) and isotopic signatures for nitrate, ammonium and PM will be measured. Primary production and uptake rates for different nitrogen substrates were also measured using in--‐situ stable isotope incubation experiments to study the change in algae growth rates. That campaign was performed in close relation with colleagues from the Institute of Marine and Antarctic Studies (Hobart, Australia) to link our findings with the availability of trace metals such as iron. Temperature profiles in the ice showed a clear change halfway the sampling campaign with increasing temperatures, likely accompanied by an increase in permeability throughout the ice. Results show a large accumulation of biomass in the bottom few 5 cm (particulate organic carbon reaching up to 1300 μmol l‐1). Preliminary data also shows a large accumulation of nitrate at the bottom with concentrations exceeding those in the underlying water. Preliminary results will be presented and discussed. [less ▲]

Detailed reference viewed: 50 (1 ULiège)
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 ▲]

Detailed reference viewed: 47 (9 ULiège)
Full Text
Peer Reviewed
See detailInfluence of short-term synoptic events and snow depth on DMS, DMSP, and DMSO dynamics in Antarctic spring sea ice
Carnat, Gauthier; Brabant, Frédéric; Dumont, Isabelle et al

in Elementa: Science of the Anthropocene (2016), 4(0), 000135

Temporal changes in the concentration profiles of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), and dimethylsulfoxide (DMSO) were measured in pack ice from the Bellingshausen Sea (Antarctica ... [more ▼]

Temporal changes in the concentration profiles of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), and dimethylsulfoxide (DMSO) were measured in pack ice from the Bellingshausen Sea (Antarctica) during the winter-spring transition of 2007. Two sites with contrasting snow and ice thicknesses were sampled, with high concentrations of DMS, DMSP, and DMSO observed at both sites, especially in surface ice. These high concentrations were shown to correspond to the development of a surface ice microalgal community dominated by strong DMSP producers (flagellates and dinoflagellates) following flooding of the ice cover. Several short-term synoptic events were observed and shown to influence strongly the dynamics of sea ice DMS, DMSP, and DMSO. In particular, a cold spell event was associated with drastic changes in the environmental conditions for the sea ice microbial communities and to a remarkable increase in the production of dimethylated sulfur compounds at both sites. A good correlation between all dimethylated sulfur compounds, sea ice temperature, and brine salinity suggested that the observed increase was triggered mainly by increased thermal and osmotic stresses on microalgal cells. Atmospheric forcing, by controlling sea ice temperature and hence the connectivity and instability of the brine network, was also shown to constrain the transfer of dimethylated sulfur compounds in the ice towards the ocean via brine drainage. Analysis of the two contrasting sampling sites shed light on the key role played by the snow cover in the sea ice DMS cycle. Thicker snow cover, by insulating the underlying sea ice, reduced the amplitude of environmental changes associated with the cold spell, leading to a weaker physiological response and DMS, DMSP, and DMSO production. Thicker snow also hampered the development of steep gradients in sea ice temperature and brine salinity, thereby decreasing the potential for the release of dimethylated sulfur compounds to the ocean via brine drainage. [less ▲]

Detailed reference viewed: 21 (2 ULiège)
Full Text
Peer Reviewed
See detailImpacts of ikaite export from sea ice to the underlying seawater in a sea ice-seawater mesocosm
Geilfus, N.-X.; Galley, R. J.; Else, B. G. T. et al

in Cryosphere (The) (2016), 10

Ikaite precipitation within sea ice could act as a significant sink for atmospheric CO2. However, the fate of these ikaite crystals is still poorly understood. We quantify temporal inorganic carbon ... [more ▼]

Ikaite precipitation within sea ice could act as a significant sink for atmospheric CO2. However, the fate of these ikaite crystals is still poorly understood. We quantify temporal inorganic carbon dynamics from initial sea ice formation from open water to its melt during a month-long experiment in a sea ice-seawater mesocosm pool. Within sea ice, ikaite precipitation and CO2 exchange with the atmosphere were the main processes affecting inorganic carbon dynamics, while the dissolution of ikaite was the main process affecting inorganic carbon dynamics in the underlying seawater. Based on the total alkalinity (TA) and total dissolved inorganic carbon (TCO2) within sea ice and seawater, we estimated ikaite precipitated up to 167 ± 3 µmol kg-1 within sea ice; up to 57 % of the ikaite precipitated within sea ice was exported to the underlying seawater where it was dissolved. Ikaite export from the ice to the underlying seawater was associated with brine rejection during sea ice growth, increased sea ice vertical connectivity due to the upward percolation of seawater, and meltwater flushing during sea ice melt. The dissolution of the ikaite crystals in the water column kept the seawater pCO2 undersaturated compared to the atmosphere in spite of increased salinity, TA, and TCO2 associated with sea ice growth. Results indicate that ikaite export from sea ice and its dissolution in the underlying seawater can potentially hamper the effect of oceanic acidification on the aragonite saturation state (Ωaragonite) in fall and winter in ice-covered areas, at the time when Ωaragonite is smallest. [less ▲]

Detailed reference viewed: 63 (7 ULiège)
Full Text
Peer Reviewed
See detailIncorporation of iron and organic matter into young Antarctic sea ice during its initial growth stages
Janssens, Julie; Meiners, Klaus M.; Tison, Jean-Louis et al

in Elementa: Science of the Anthropocene (2016), 4(1), 000123

This study reports concentrations of iron (Fe) and organic matter in young Antarctic pack ice and during its initial growth stages in situ. Although the importance of sea ice as an Fe reservoir for ... [more ▼]

This study reports concentrations of iron (Fe) and organic matter in young Antarctic pack ice and during its initial growth stages in situ. Although the importance of sea ice as an Fe reservoir for oceanic waters of the Southern Ocean has been clearly established, the processes leading to the enrichment of Fe in sea ice have yet to be investigated and quantified. We conducted two in situ sea-ice growth experiments during a winter cruise in the Weddell Sea. Our aim was to improve the understanding of the processes responsible for the accumulation of dissolved Fe (DFe) and particulate Fe (PFe) in sea ice, and of particulate organic carbon and nitrogen, dissolved organic carbon, extracellular polymeric substances, inorganic macro-nutrients (silicic acid, nitrate and nitrite, phosphate and ammonium), chlorophyll a and bacteria. Enrichment indices, calculated for natural young ice and ice newly formed in situ, indicate that during Antarctic winter all of the measured forms of particulate matter were enriched in sea ice compared to underlying seawater, and that enrichment started from the initial stages of sea-ice formation. Some dissolved material (DFe and ammonium) was also enriched in the ice but at lower enrichment indices than the particulate phase, suggesting that size is a key factor for the incorporation of impurities in sea ice. Low chlorophyll a concentrations and the fit of the macro-nutrients (with the exception of ammonium) with their theoretical dilution lines indicated low biological activity in the ice. From these and additional results we conclude that physical processes are the dominant mechanisms leading to the enrichment of DFe, PFe, organic matter and bacteria in young sea ice, and that PFe and DFe are decoupled during sea-ice formation. Our study thus provides unique quantitative insight into the initial incorporation of impurities, in particular DFe and PFe, into Antarctic sea ice. [less ▲]

Detailed reference viewed: 61 (3 ULiège)
Full Text
Peer Reviewed
See detailAssessment of the sea-ice carbon pump: Insights from a three-dimensional ocean-sea-ice biogeochemical model (NEMO-LIM-PISCES)
Moreau, Sébastien; Vancoppenolle, Martin; Bopp, Laurent et al

in Elementa: Science of the Anthropocene (2016), 4(1), 000122

The role of sea ice in the carbon cycle is minimally represented in current Earth System Models (ESMs). Among potentially important flaws, mentioned by several authors and generally overlooked during ESM ... [more ▼]

The role of sea ice in the carbon cycle is minimally represented in current Earth System Models (ESMs). Among potentially important flaws, mentioned by several authors and generally overlooked during ESM design, is the link between sea-ice growth and melt and oceanic dissolved inorganic carbon (DIC) and total alkalinity (TA). Here we investigate whether this link is indeed an important feature of the marine carbon cycle misrepresented in ESMs. We use an ocean general circulation model (NEMO-LIM-PISCES) with sea-ice and marine carbon cycle components, forced by atmospheric reanalyses, adding a first-order representation of DIC and TA storage and release in/from sea ice. Our results suggest that DIC rejection during sea-ice growth releases several hundred Tg C yr−1 to the surface ocean, of which < 2% is exported to depth, leading to a notable but weak redistribution of DIC towards deep polar basins. Active carbon processes (mainly CaCO3 precipitation but also ice-atmosphere CO2 fluxes and net community production) increasing the TA/DIC ratio in sea-ice modified ocean-atmosphere CO2 fluxes by a few Tg C yr−1 in the sea-ice zone, with specific hemispheric effects: DIC content of the Arctic basin decreased but DIC content of the Southern Ocean increased. For the global ocean, DIC content increased by 4 Tg C yr−1 or 2 Pg C after 500 years of model run. The simulated numbers are generally small compared to the present-day global ocean annual CO2 sink (2.6 ± 0.5 Pg C yr−1 ). However, sea-ice carbon processes seem important at regional scales as they act significantly on DIC redistribution within and outside polar basins. The efficiency of carbon export to depth depends on the representation of surface-subsurface exchanges and their relationship with sea ice, and could differ substantially if a higher resolution or different ocean model were used. [less ▲]

Detailed reference viewed: 39 (4 ULiège)
See detailWintertime bacterial communities in changing Antarctic sea ice
Eronen-Rasimus, E.; Luhtanen, A.-M.; Delille, Bruno ULiege et al

Poster (2016, August)

Detailed reference viewed: 14 (1 ULiège)
See detailPhage-host systems isolated from sea ice
Luhtanen, A.-M.; Rintala, J.-M.; Oksanen, H. et al

Poster (2016, August)

Detailed reference viewed: 21 (1 ULiège)
Full Text
Peer Reviewed
See detailMassive marine methane emissions from near-shore shallow coastal areas
Borges, Alberto ULiege; Champenois, Willy ULiege; Gypens, N et al

in Scientific Reports (2016), 6

Methane is the second most important greenhouse gas contributing to climate warming. The open ocean is a minor source of methane to the atmosphere. We report intense methane emissions from the near-shore ... [more ▼]

Methane is the second most important greenhouse gas contributing to climate warming. The open ocean is a minor source of methane to the atmosphere. We report intense methane emissions from the near-shore southern region of the North Sea characterized by the presence of extensive areas with gassy sediments. The average flux intensities (~130 μmol m−2 d−1) are one order of magnitude higher than values characteristic of continental shelves (~30 μmol m−2 d−1) and three orders of magnitude higher than values characteristic of the open ocean (~0.4 μmol m−2 d−1). The high methane concentrations (up to 1,128 nmol L−1) that sustain these fluxes are related to the shallow and well-mixed water column that allows an efficient transfer of methane from the seafloor to surface waters. This differs from deeper and stratified seep areas where there is a large decrease of methane between bottom and surface by microbial oxidation or physical transport. Shallow well-mixed continental shelves represent about 33% of the total continental shelf area, so that marine coastal methane emissions are probably under-estimated. Near-shore and shallow seep areas are hot spots of methane emission, and our data also suggest that emissions could increase in response to warming of surface waters. [less ▲]

Detailed reference viewed: 142 (10 ULiège)