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

in Journal of Geophysical Research. Oceans (2014), 119

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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