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See detailDrivers of inorganic carbon dynamics in first-year sea ice: A model study
Moreau, S.; Vancoppenolle, M.; Delille, Bruno ULg 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 detailUsing stable isotopes to unravel the role of sea-ice in the methane cycle
Sapart, C.J.; Zhou, Jiayun; Carnat, G. et al

Conference (2015, May 16)

Methane plays an important role in the Earth’s climate system. The atmospheric methane concentration has increased in concert with the industrialization, but since the mid 80’s the methane growth rate ... [more ▼]

Methane plays an important role in the Earth’s climate system. The atmospheric methane concentration has increased in concert with the industrialization, but since the mid 80’s the methane 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 methane cycle, especially in the Arctic regions, which are highly vulnerable to climate change and contain large methane reservoirs. Recently, an unexpected methane excess has been reported above Arctic sea-ice showing that sea-ice might play a significant role in the methane cycle. Nonetheless, the nature of the process leading to methane 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 methane excess above sea-ice. We performed methane isotope (d13C and dD) analyses on sea-ice samples, as well as geochemical measurements, to determine the possible pathways involved in methane 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. It has long been thought that methane present in sea-water would oxidize in or under the sea ice, but our first stable isotope sea ice profiles show no significant oxidation pattern. On the other hand, we show that landfast sea ice from both the shallow-shelf of Barrow and our deeper Southern Ocean site is supersaturated in methane and that under specific conditions methane is likely formed in the ice. [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 ULg 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 detailMeasurements of air-ice CO2 fluxes over artificial sea ice emphasize the role of bubbles in gas transport
Kotovitch, Marie ULg; Moreau, Sébastion; Zhou, Jiayun et al

Poster (2015, March)

Detailed reference viewed: 32 (4 ULg)
See detailImaging air filled porosity in sea ice cover: Implication for sea ice permeability and gas exchange at the ice-atmosphere interface
Crabeck, O,; Galley, R,; Else, B, et al

Poster (2015, March)

Detailed reference viewed: 33 (0 ULg)
See detailPhotosynthesis-irradiance response curves revealed active sympagic communities in the Weddell Sea Winter, 2013
Rintala, J.-M.; Luhtanen, A.-M.; Enberg, S. et al

Poster (2015, March)

Detailed reference viewed: 27 (0 ULg)
See detailBlue sky and green bugs – How physical parameters and algal speciation influence DMSP and DMS profiles in Antarctic winter sea ice
Uhlig, C.; Rintala, J.-M.; Tison, J.-L. et al

Poster (2015, March)

Detailed reference viewed: 14 (0 ULg)
See detailThe role of sea ice in the carbon cycle of Polar Seas: 1D to 3D modelling
Moreau, S.; Vancoppenolle, M.; Delille, Bruno ULg et al

Poster (2015, March)

Detailed reference viewed: 24 (5 ULg)
See detailIsolation of cultivable viruses from Antarctic wintertime sea ice
Luhtanen, A.-M.; Bamford, D.; De Jong, J. et al

Poster (2015, March)

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

Poster (2015, March)

Detailed reference viewed: 30 (7 ULg)
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See detailDrivers of inorganic carbon dynamics in first-year sea ice: A model study.
Moreau, Sebastien; Vancoppenolle, Martin; Delille, Bruno ULg et al

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

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

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

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See detailMid-winter freeze experiment in the Arctic Ocean: Norwegian Young sea ICE cruise (N-ICE2015)
Nomura, Daiki; Granskog, Mats A.; Fransson, Agneta et al

Poster (2014, December 02)

In mid-January 2015, RV Lance will freeze into the ice north of Svalbard, Arctic Ocean at around 83.25°N 30°E, and passively drift with the ice as part of the Norwegian Young sea ICE cruise (N-ICE2015 ... [more ▼]

In mid-January 2015, RV Lance will freeze into the ice north of Svalbard, Arctic Ocean at around 83.25°N 30°E, and passively drift with the ice as part of the Norwegian Young sea ICE cruise (N-ICE2015). Judging from historic sea ice drift trajectories, it is likely that RV Lance will drift in a SW direction and the ship will probably be freed from the ice in mid spring after about two to three months of drift. Thereafter, RV Lance will return to her starting position and start a new drift. Under all circumstances, the ice drift project will end in late June 2015. Throughout the cruise the focus will be on the interaction of the atmosphere-ice-ocean system and the response of the marine ecosystem to the thinner ice regime. The overall goal of the project team is to improve our understanding of the role of the younger ice pack in the Arctic on greenhouse gas fluxes and to ultimately assess whether the Arctic Ocean is a sink or source of greenhouse gases. We plan to conduct long-term synchronous observations of Arctic snow and sea ice biogeochemistry and physics and fluxes of carbon dioxide, methane, nitrous oxide and bromoform. This work targets at filling a crucial gap in our understanding of the role of Arctic sea ice in the climate system. This is done by conducting state of the art observations on Arctic sea ice in the polar night, when observations are basically non-existent. Further we are focusing on the new thinner ice regime, which is even less documented. We aim to understand how the thinner sea ice in the Arctic basin contributes (i) to important greenhouse gas exchange between the atmosphere and ocean and (ii) to aerosol formation, that contribute to the radiative balance of the planet. This work will increase direct collaboration between Japanese and European scientists in the Arctic, and combines complimentary expertise and experience from several international partners to carry out the interdisciplinary work proposed. [less ▲]

Detailed reference viewed: 84 (2 ULg)
See detailAtmosphere - surface fluxes estimated from different measurement techniques over snow covered sea ice
Sørensen, L.L; Delille, Bruno ULg; Jensen, B. et al

Conference (2014, December)

Carbon dioxide flux measurements in ecosystem science are mostly conducted over terrestrial areas by eddy covariance technique or the closed chamber method. Both methods are becoming more frequently used ... [more ▼]

Carbon dioxide flux measurements in ecosystem science are mostly conducted over terrestrial areas by eddy covariance technique or the closed chamber method. Both methods are becoming more frequently used over ice and snow covered surfaces. Comparisons between eddy covariance and chamber methods have been carried out over terrestrial surfaces, but carefully designed inter calibration experiments over sea ice and snow are still needed to assess differences and uncertainties. Here we present one of the first comparisons of fluxes over snow covered sea ice estimated from the eddy covariance technique and the chamber method. The measurements were carried out at Young Sound in Northeast Greenland from May 28th to June 28th 2014 starting just before snow started to melt. The comparison shows in general higher fluxes obtained by the eddy covariance method however the disagreement varies depending on meteorological and surface parameters. The flux divergence in relation to varying parameters will be presented and possible causes will be discussed. [less ▲]

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

in Marine Chemistry (2014), 166

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

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

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

Poster (2014, October)

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

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

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See detailCO2 fluxes across the air-ice interface
Delille, Bruno ULg

Conference (2014, July)

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See detailUsuing the Arctic Environment Test Basin to study the dynamics of dissolved organic matter in sea ice
Thomas, D.N.; Zhou, Jiayun ULg; Kaartokallio, H. et al

Conference (2014, July)

This is a report from the INTERICE 5 project that used the Arctic Environment Test Basin at HSVA from 21 May to 19 June 2012. The overarching aim was to investigate the physical and biological controls of ... [more ▼]

This is a report from the INTERICE 5 project that used the Arctic Environment Test Basin at HSVA from 21 May to 19 June 2012. The overarching aim was to investigate the physical and biological controls of dissolved organic matter incorporation into growing sea ice and the effect of melting once the ice had consolidated. Measurements were also made on the CO2 fluxes at the ice surface in relation to the chemical and biological changes taking place in the ice. The Interice 5 team was a multidisciplinary group of glaciologists, chemists and microbiologists from Belgium, Denmark, Finland, Germany and U.K. They were able to build on the experiences of previous INTERICE 2, 3 & 4 projects to maximize the opportunities from the facility. The preliminary results from the experiment will be presented, in the context of what is known about these processes from field campaigns. [less ▲]

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See detailPhysical controls on the storage of methane in landfast sea ice
Zhou, Jiayun ULg; Tison, J.-L.; Carnat, G. et al

in Cryosphere (The) (2014), 8(3), 1019-1029

We report on methane (CH4) dynamics in landfast sea ice, brine and under-ice seawater at Barrow in 2009. The CH4 concentrations in under-ice water ranged between 25.9 and 116.4 nmol L-1sw, indicating a ... [more ▼]

We report on methane (CH4) dynamics in landfast sea ice, brine and under-ice seawater at Barrow in 2009. The CH4 concentrations in under-ice water ranged between 25.9 and 116.4 nmol L-1sw, indicating a supersaturation of 700 to 3100 % relative to the atmosphere. In comparison, the CH4 concentrations in sea ice, ranged between 3.4 and 17.2 nmol L-1ice, and the deduced CH4 concentrations in brine, between 13.2 and 677.7 nmol L-1brine. We investigated on the processes explaining the difference in CH4 concentrations between sea ice, brine and the under-ice water, and suggest that biological controls on the storage of CH4 in ice was minor in comparison to the physical controls. Two physical processes regulated the storage of CH4 in our landfast ice samples: bubble formation within the ice and sea ice permeability. Gas bubble formation from solubility changes had favoured the accumulation of CH4 in the ice at the beginning of ice growth. CH4 retention in sea ice was then twice as efficient as that of salt; this also explains the overall higher CH4 concentrations in brine than in the under-ice water. As sea ice thickened, gas bubble formation became less efficient, CH4 was then mainly trapped in the dissolved state. The increase of sea ice permeability during ice melt marked the end of CH4 storage. [less ▲]

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See detailSnow cover and short-term synoptic events drive biogeochemical dynamics in winter Weddell Sea pack ice (AWECS cruise - June to August 2013)
Tison, J.-L.; Delille, Bruno ULg; Dieckmann, G. et al

Conference (2014, March)

This paper presents the preliminary results of an integrated multidisciplinary study of pack ice biogeochemistry in the Weddell Sea during the winter 2013 (June-August). The sea ice biogeochemistry group ... [more ▼]

This paper presents the preliminary results of an integrated multidisciplinary study of pack ice biogeochemistry in the Weddell Sea during the winter 2013 (June-August). The sea ice biogeochemistry group was one of the components of the AWECS (Antarctic Winter Ecosystem and Climate Study) cruise (Polarstern ANTXXIX-6). A total of 12 stations were carried out by the sea ice biogeochemistry group, which collected a suite of variables in the fields of physics, inorganic chemistry, gas content and composition, microbiology, biogeochemistry, trace metals and the carbonate system in order to give the best possible description of the sea ice cover and its interactions at interfaces. Samples were collected in the atmosphere above (gas fluxes), in the snow cover, in the bulk ice (ice cores), in the brines (sackholes) and in the sea water below (0m, 1m, 30 m). Here we present the results of basic physico-chemical (T°, bulk ice salinity, brine volumes, brine salinity, Rayleigh numbers) and biological (Chla) measurements in order to give an overview of the general status of the Weddell Sea winter pack ice encountered, and discuss how it controls climate relevant biogeochemical processes. Our results from the first set of 9 stations, mainly sampled along the Greenwich meridian and the easternmost part of the Weddell Sea definitively refute the view of a biogeochemically “frozen” sea ice during the Winter. This has already been demonstrated for the Spring and Summer, but we now see that sea ice sustains considerable biological stocks and activities throughout the Winter, despite the reduced amount of available PAR radiation. Accretion of the snow cover appears to play an essential role in driving biogeochemical activity, through warming from insulation, thus favouring brine transport, be it through potential convection, surface brine migration (brine tubes) or flooding. This results in a “widening” of the internal autumn layer (quite frequent in this rafting-dominated sea ice cover) and increase of the chla burden with age. Results from the second set of 3 stations in the western branch of the Weddell Sea gyre confirm that it comprises a mixture of older fast/second year ice floes with younger first-year ice floes. The older ice had the highest Chla concentrations of the entire cruise (>200 mgl-1), in an internal community enclosed within desalinized impermeable upper and lower layers. The first-year ice differs from that in the eastern Weddell Sea as it is dominated by columnar ice and (weak) algal communities are only found on the bottom or near the surface (no internal maximum). [less ▲]

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