References of "Zhou, Jiayun"
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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 The Cryosphere (in press)

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 detailPhysical and biological controls on DMS,P dynamics in ice-shelf influenced fast ice during a winter-spring and a spring-summer transitions
Carnat, G.; Zhou, Jiayun ULg; Papakyriakou, T. et al

in Journal of Geophysical Research. Oceans (in press)

We report the seasonal and vertical variations of dimethylsulphide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) in fast ice at Cape Evans, McMurdo Sound (Antarctica) during the spring-summer ... [more ▼]

We report the seasonal and vertical variations of dimethylsulphide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) in fast ice at Cape Evans, McMurdo Sound (Antarctica) during the spring-summer transition in 2011 and winter-spring transition in 2012. We compare the variations of DMS,P observed to the seasonal evolution of the ice algal biomass and of the physical properties of the ice cover, with emphasis on the ice texture and brine dynamics. Isolated DMS and DMSP maxima were found during both seasonal episodes in interior ice and corresponded to the occurrence of platelet crystals in the ice texture. We show that platelet crystals formation corresponded in time and depth to the incorporation of dinoflagellates (strong DMSP producers) in the ice cover. We also show that platelet crystals could modify the environmental stresses on algal cells and perturb the vertical redistribution of DMS,P concentrations. We show that during the winter-spring transition in 2012, the DMS,P profiles were strongly influenced by the development and decline of a diatom dominated bloom in the bottom ice, with DMSP variations remarkably following chl a variations. During the spring-summer transition in 2011, the increase in brine volume fraction (influencing ice permeability) on warming was shown to trigger (1) an important release of DMS to the under-ice water through brine convection (2) a vertical redistribution of DMSP across the ice [less ▲]

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

Conference (2014, March)

YROSIAE survey aimed to carry out a year-round survey of land-fast sea ice focusing on the study of sea ice physics and biogeochemistry in order to a) better understand and budget exchanges of energy and ... [more ▼]

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

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See detailOn the use of O2/Ar and O2/N2 to estimate the biological carbon uptake in landfast sea ice
Zhou, Jiayun ULg; Delille, Bruno ULg; Brabant, F. et al

Poster (2014, March)

Sea ice is one of the largest biomes on Earth. The net community production (NCP) of the microorganisms living in sea ice impacts the dynamics of pCO2 in sea ice, and therefore the CO2 exchanges at the ... [more ▼]

Sea ice is one of the largest biomes on Earth. The net community production (NCP) of the microorganisms living in sea ice impacts the dynamics of pCO2 in sea ice, and therefore the CO2 exchanges at the air-ice-sea interfaces. As oxygen O2 and carbon C are both involved in the photosynthetic and respiration processes, one can theoretically assess NCP (in terms of C uptake) from O2 measurements. However, the concentration of O2 in sea ice depends not only on biological processes (i.e., NCP) but also on physical processes. We present a technique for assessing NCP in sea ice, based on the use of the O2/Ar ratio, which should correct for the physical contribution in O2 variations. We also compare the use of O2/Ar and O2/N2 for deriving NCP, and demonstrate that O2/Ar is more suitable, as it is more sensitive and less affected by gas diffusion and gas bubble formation during sea ice growth and decay than O2/N2. Using O2/Ar, we then provide conservative estimates of NCP in landfast sea ice, from ice cores collected in Barrow, from January through June 2009. The minimum estimate of the NCP in the whole ice cover reached 229 mg C.m-².d-1 in late spring. This is about 20 times higher than the atmospheric C uptake at that time identified from CO2 fluxes measurements at the ice-air interface, and therefore indicates that the main source of C used in the NCP was from the under-ice water. [less ▲]

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See detailFactors driving pCO2 dynamics in sea ice during a large-scale ice tank experiment
Zhou, Jiayun ULg; Delille, Bruno ULg; Tison, J.-L. et al

Conference (2014, March)

According to previous studies, pCO2 fluxes measured over Arctic sea ice are higher than those measured over Antarctic sea ice. We hypothesized that this was due to enhanced respiration in Arctic sea ice ... [more ▼]

According to previous studies, pCO2 fluxes measured over Arctic sea ice are higher than those measured over Antarctic sea ice. We hypothesized that this was due to enhanced respiration in Arctic sea ice, as a consequence of higher riverine inputs of dissolved organic carbon (DOC) into Arctic seawater. We tested this hypothesis during the Interice V experiment at the HSVA (Hamburg) environmental test basin facility. We reproduced the growth and decay cycle of sea ice in replicate mesocosms (1 m3) filled with North Sea water (NSW series), and compared these with another series of mesocosms to which humic-rich river water had been added (10%) to increase the DOC concentration (R series). Primary producers were excluded from the experiment. The evolution of the temperature, salinity, DOC, pCO2 and bacterial biomass and production were measured in ice sampled at regular intervals throughout the experiment, as well as in the under-ice water. In addition, ice-air pCO2 fluxes were continuously monitored over both NSW and R mesocosms. pCO2 values in ice were higher in the R ice than in the NSW ice. This is attributed to the DOC content and bacterial respiration, rather than to the ice physical properties (i.e., ice permeability constrained by the ice temperature and salinity). Indeed, R ice had higher DOC content and bacterial production than the NSW ice while both showed similar physical properties. The evolution of the ice-air pCO2 fluxes was consistent with the evolution of pCO2 in ice. The fluxes were, as expected, positive (from sea ice to the atmosphere) during ice growth and negative (from the atmosphere to the ice) during ice melt. [less ▲]

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See detailBiological and physical controls on DMS,P dynamics in ice-shelf-influenced fast ice
Carnat, G.; Zhou, Jiayun ULg; Papakyriakou, T. et al

Conference (2014, March)

Dimethylsulfide (DMS) is a volatile sulphur compound produced by the degradation of dimethylsulphoniopropionate (DMSP), a metabolite synthesized by microalgae as i.a. cryoprotectant and osmoregulator. It ... [more ▼]

Dimethylsulfide (DMS) is a volatile sulphur compound produced by the degradation of dimethylsulphoniopropionate (DMSP), a metabolite synthesized by microalgae as i.a. cryoprotectant and osmoregulator. It is also an important climate-active gas, being the primary source of marine-derived sulphate aerosols which play an important role in the earth-atmosphere radiation balance. In the last two decades, there has been an increasing interest in the role of the marine cryosphere in the DMS,P cycle, motivated by repeated observations of very high DMS,P concentrations in sea ice. However, our understanding of the factors driving the spatiotemporal variations of these high concentrations, and hence the fate of the sea ice DMS pool, remains limited. To date, studies have essentially focused on biotic factors, attributing the high DMS,P concentrations to the high biomass of the sympagic communities, and to their strong physiological response to the low temperature and high salinity stresses of the brine habitat. We present here an approach integrating both biotic and abiotic factors, as we investigate the influence of sea ice growth processes and brine dynamics on the DMS,P cycle. We focus on a fast ice site (Cape Evans, McMurdo Sound, Antarctica) under the influence of ice-shelf waters, and provide measurements covering a full cycle of ice growth. We show a good correspondence between isolated maxima of DMS,P in interior ice and the occurrence of platelet crystals in the ice texture. We develop the idea that platelet ice formation in May strongly modifies the production of DMS,P by (1) favoring the incorporation of strong DMSP producers and by (2) exposing these producers to stronger environmental stresses. We then show the influence of the development and decline of a strong diatom bloom from October to November on bottom ice DMS,P concentrations. Finally, we show that the increase in brine volume fraction (permeability) on warming in early December triggers (1) an important release of DMS to the ocean through brine convection, and (2) a vertical redistribution of DMSP across the ice. [less ▲]

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See detailUsing stable isotopes to unravel the role of sea-ice in the methane cycle
Sapart, C.J.; Zhou, Jiayun ULg; Niemann, T et al

Poster (2014, March)

Methane (CH4) plays an important role in the Earth’s climate system. The atmospheric CH4 concentration has increased in concert with the industrialization, but since the mid 80’s the CH4 growth rate ... [more ▼]

Methane (CH4) plays an important role in the Earth’s climate system. The atmospheric CH4 concentration has increased in concert with the industrialization, but since the mid 80’s the CH4 growth rate decreased to reach a near-zero level in 2000 and started to increase again from 2007 on. However, the underlying variations in sources and/or sinks that cause these variations are to date not well understood. To predict future climate, it is essential to unravel the processes controlling the CH4 cycle, especially in the Arctic regions, which are highly vulnerable to climate change and contain large CH4 reservoirs. Recently, an unexpected CH4 excess has been reported above Arctic sea-ice showing that sea-ice might play a significant role in the CH4 cycle. Nonetheless, the nature of the process leading to CH4 production in or nearby sea-ice has not yet been identified. We applied a new multi-proxy approach merging atmospheric chemistry, glaciology and biogeochemistry to understand and quantify the processes responsible for the CH4 excess above sea-ice. We performed CH4 isotope (13C and D) analyses on sea-ice samples, as well as microbial (lipid biomarkers) and geochemical measurements, to determine the possible pathways involved in CH4 production and removal in or nearby sea-ice. We will present results from sea-ice samples drilled above the shallow-shelf in Barrow (Alaska) from January to June 2009 as well as above deep Southern Ocean locations in 2013. Those results allow investigating the seasonality and spatial variability in methane formation and removal pathways associated to the methane enclosed in sea-ice. [less ▲]

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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 ULg 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 detailPhysical and biogeochemical properties in landfast sea ice (Barrow, Alaska): insights on brine and gas dynamics across seasons
Zhou, Jiayun ULg; Delille, Bruno ULg; Eicken, H. et al

in Journal of Geophysical Research (2013), 118(6), 3172-3189

The impacts of the seasonal evolution of sea-ice physical properties on ice-ocean biogeochemical exchanges were investigated in landfast ice at Barrow (Alaska) from January through June 2009. Three stages ... [more ▼]

The impacts of the seasonal evolution of sea-ice physical properties on ice-ocean biogeochemical exchanges were investigated in landfast ice at Barrow (Alaska) from January through June 2009. Three stages of brine dynamics across the annual cycle have been identified based on brine salinity, brine volume fraction and porous medium Rayleigh number [less ▲]

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See detailInvestigations on physical and textural properties of Arctic first-year sea ice in the Amundsen Gulf, Canada, November 2007–June 2008 (IPY-CFL system study)
Carnat, Gauthier; Papakyriakou, Timothy; Geilfus, Nicolas-Xavier et al

in Journal of Glaciology (2013), 59(217),

We report sea-ice temperature and bulk salinity measurements as well as textural analysis from 33 first-year drift- and fast-ice stations sampled between November 2007 and June 2008 in the southern ... [more ▼]

We report sea-ice temperature and bulk salinity measurements as well as textural analysis from 33 first-year drift- and fast-ice stations sampled between November 2007 and June 2008 in the southern Beaufort Sea–Amundsen Gulf, Canadian Arctic, during the International Polar Year Circumpolar Flaw Lead (IPY-CFL) system study. We use this significant dataset to investigate the halothermodynamic evolution of sea ice from growth to melt. A strong desalination phase is observed over a small time window in the spring. Using calculated proxies of sea-ice permeability (brine volume fraction) and of the intensity of brine convection (Rayleigh number) we demonstrate that this phase corresponds to full-depth gravity drainage initiated by a restored connectivity of the brine network with warming in the spring. Most stations had a textural sequence typical of Arctic first-year ice, with granular ice overlying columnar ice. Unusual textural features were observed sporadically: sandwiched granular ice, platelet ice and draped platelet ice. We suggest that turbulence in leads and double diffusion in strong brine plumes following the refreeze of cracks are plausible mechanisms for the formation of these textures. [less ▲]

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See detailGas migration in sea ice: from observations to modelling
Zhou, Jiayun ULg; Moreau, Sébastien; Vancoppenolle, Martin et al

Poster (2012, May 07)

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See detailHow convection and diffusion processes might affect biological imprints, a challenge for modelers
Tison, J.-L.; Zhou, Jiayun ULg; Thomas, D. et al

Conference (2012, April)

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See detailTemporal evolution of biogeochemical properties of landfast sea ice at Barrow (Alaska)
Zhou, Jiayun ULg; Tison, Jean-Louis; Eicken, Hajo et al

Poster (2011, March)

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See detailA multidisciplinary approach to understanding the sea ice system: implications on gas. Gordon Research Seminars
Zhou, Jiayun ULg; Tison, Jean-Louis; Eicken, Hajo et al

Conference (2011, March)

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See detailGas concentrations in Barrow landfast sea ice: the winter/spring contrasts
Zhou, Jiayun ULg; Tison, Jean-Louis; Brabant, Frédéric et al

in Solas News (2011), 13(Summer), 22-23

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See detailOverview of CO2 dynamics within sea ice
Delille, Bruno ULg; Geilfus, N.; Vancoppenolle, M. et al

Conference (2011)

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