Tison
Jean-Louis
Tison
Jean-Louis
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ArticleCO2 deposition over the multi-year ice of the western Weddell Sea(American Geophysical Union, 2006-07-13) Zemmelink, Hendrik J. ; Delille, Bruno ; Tison, Jean-Louis ; Hintsa, Eric J. ; Houghton, Leah A. ; Dacey, John W. H.Field measurements by eddy correlation (EC) indicate an average uptake of 0.6 g CO2 m−2 d−1 by the ice-covered western Weddell Sea in December 2004. At the same time, snow that covers ice floes of the western Weddell Sea becomes undersaturated with CO2 relative to the atmosphere during early summer. Gradients of CO2 from the ice to the atmosphere do not support significant diffusive fluxes and are not strong enough to explain the observed CO2 deposition. We hypothesize that the transport of air through the snow pack is controlled by turbulence and that undersaturation of CO2 is caused by biological productivity at the ice-snow and snow-atmosphere interface. The total carbon uptake by the multi-year ice zone of the western Weddell Sea in December could have been as high as 6.6 Tg C y−1.
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ArticlePhysical and biological properties of early winter Antarctic sea ice in the Ross Sea.(Cambridge University Press, 2020-06-24) Tison, Jean-Louis ; Maksym, Ted ; Fraser, Alexander D. ; Corkill, Matthew ; Kimura, Noriaki ; Nosaka, Yuichi ; Nomura, Daiki ; Vancoppenolle, Martin ; Ackley, Stephen ; Stammerjohn, Sharon E. ; Wauthy, Sarah ; Van der Linden, Fanny ; Carnat, Gauthier ; Sapart, Célia ; de Jong, Jeroen ; Fripiat, Francois ; Delille, BrunoThis work presents the results of physical and biological investigations at 27 biogeochemical stations of early winter sea ice in the Ross Sea during the 2017 PIPERS cruise. Only two similar cruises occurred in the past, in 1995 and 1998. The year 2017 was a specific year, in that ice growth in the Central Ross Sea was considerably delayed, compared to previous years. These conditions resulted in lower ice thicknesses and Chl-a burdens, as compared to those observed during the previous cruises. It also resulted in a different structure of the sympagic algal community, unusually dominated by Phaeocystis rather than diatoms. Compared to autumn-winter sea ice in the Weddell Sea (AWECS cruise), the 2017 Ross Sea pack ice displayed similar thickness distribution, but much lower snow cover and therefore nearly no flooding conditions. It is shown that contrasted dynamics of autumnal-winter sea-ice growth between the Weddell Sea and the Ross Sea impacted the development of the sympagic community. Mean/median ice Chl-a concentrations were 3–5 times lower at PIPERS, and the community status there appeared to be more mature (decaying?), based on Phaeopigments/Chl-a ratios. These contrasts are discussed in the light of temporal and spatial differences between the two cruises.
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ArticleSea-ice production and air/ice/ocean/biogeochemistry interactions in the Ross Sea during the PIPERS 2017 autumn field campaign(Cambridge University Press, 2020-06-11) Ackley, Stephen ; Stammerjohn, Sharon E. ; Maksym, Ted ; Smith, Madison M. ; Cassano, John ; Guest, Peter ; Tison, Jean-Louis ; Delille, Bruno ; Loose, Brice ; Sedwick, Peter N. ; De Pace, Lisa ; Roach, Lettie ; Parno, JulieThe Ross Sea is known for showing the greatest sea-ice increase, as observed globally, particularly from 1979 to 2015. However, corresponding changes in sea-ice thickness and production in the Ross Sea are not known, nor how these changes have impacted water masses, carbon fluxes, biogeochemical processes and availability of micronutrients. The PIPERS project sought to address these questions during an autumn ship campaign in 2017 and two spring airborne campaigns in 2016 and 2017. PIPERS used a multidisciplinary approach of manned and autonomous platforms to study the coupled air/ice/ocean/biogeochemical interactions during autumn and related those to spring conditions. Unexpectedly, the Ross Sea experienced record low sea ice in spring 2016 and autumn 2017. The delayed ice advance in 2017 contributed to (1) increased ice production and export in coastal polynyas, (2) thinner snow and ice cover in the central pack, (3) lower sea-ice Chl-a burdens and differences in sympagic communities, (4) sustained ocean heat flux delaying ice thickening and (5) a melting, anomalously southward ice edge persisting into winter. Despite these impacts, airborne observations in spring 2017 suggest that winter ice production over the continental shelf was likely not anomalous.