Delille Bruno

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Delille
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Bruno
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  • Article
    CO2 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.
  • Article
    Constraining Southern Ocean air-sea-ice fluxes through enhanced observations
    (Frontiers Media, 2019-07-31) Swart, Sebastiaan ; Gille, Sarah T. ; Delille, Bruno ; Josey, Simon A. ; Mazloff, Matthew R. ; Newman, Louise ; Thompson, Andrew F. ; Thomson, James M. ; Ward, Brian ; du Plessis, Marcel ; Kent, Elizabeth ; Girton, James B. ; Gregor, Luke ; Heil, Petra ; Hyder, Patrick ; Pezzi, Luciano Ponzi ; de Souza, Ronald Buss ; Tamsitt, Veronica ; Weller, Robert A. ; Zappa, Christopher J.
    Air-sea and air-sea-ice fluxes in the Southern Ocean play a critical role in global climate through their impact on the overturning circulation and oceanic heat and carbon uptake. The challenging conditions in the Southern Ocean have led to sparse spatial and temporal coverage of observations. This has led to a “knowledge gap” that increases uncertainty in atmosphere and ocean dynamics and boundary-layer thermodynamic processes, impeding improvements in weather and climate models. Improvements will require both process-based research to understand the mechanisms governing air-sea exchange and a significant expansion of the observing system. This will improve flux parameterizations and reduce uncertainty associated with bulk formulae and satellite observations. Improved estimates spanning the full Southern Ocean will need to take advantage of ships, surface moorings, and the growing capabilities of autonomous platforms with robust and miniaturized sensors. A key challenge is to identify observing system sampling requirements. This requires models, Observing System Simulation Experiments (OSSEs), and assessments of the specific spatial-temporal accuracy and resolution required for priority science and assessment of observational uncertainties of the mean state and direct flux measurements. Year-round, high-quality, quasi-continuous in situ flux measurements and observations of extreme events are needed to validate, improve and characterize uncertainties in blended reanalysis products and satellite data as well as to improve parameterizations. Building a robust observing system will require community consensus on observational methodologies, observational priorities, and effective strategies for data management and discovery.
  • Article
    Polar ocean observations: A critical gap in the observing system and its effect on environmental predictions from hours to a season
    (Frontiers Media, 2019-08-06) Smith, Gregory C. ; Allard, Richard ; Babin, Marcel ; Bertino, Laurent ; Chevallier, Matthieu ; Corlett, Gary ; Crout, Julia ; Davidson, Fraser J. M. ; Delille, Bruno ; Gille, Sarah T. ; Hebert, David ; Hyder, Patrick ; Intrieri, Janet ; Lagunas, José ; Larnicol, Gilles ; Kaminski, Thomas ; Kater, Belinda ; Kauker, Frank ; Marec, Claudie ; Mazloff, Matthew R. ; Metzger, E. Joseph ; Mordy, Calvin W. ; O’Carroll, Anne ; Olsen, Steffen M. ; Phelps, Michael W. ; Posey, Pamela ; Prandi, Pierre ; Rehm, Eric ; Reid, Philip C. ; Rigor, Ignatius ; Sandven, Stein ; Shupe, Matthew ; Swart, Sebastiaan ; Smedstad, Ole Martin ; Solomon, Amy ; Storto, Andrea ; Thibaut, Pierre ; Toole, John M. ; Wood, Kevin R. ; Xie, Jiping ; Yang, Qinghua ; WWRP PPP Steering Group
    There is a growing need for operational oceanographic predictions in both the Arctic and Antarctic polar regions. In the former, this is driven by a declining ice cover accompanied by an increase in maritime traffic and exploitation of marine resources. Oceanographic predictions in the Antarctic are also important, both to support Antarctic operations and also to help elucidate processes governing sea ice and ice shelf stability. However, a significant gap exists in the ocean observing system in polar regions, compared to most areas of the global ocean, hindering the reliability of ocean and sea ice forecasts. This gap can also be seen from the spread in ocean and sea ice reanalyses for polar regions which provide an estimate of their uncertainty. The reduced reliability of polar predictions may affect the quality of various applications including search and rescue, coupling with numerical weather and seasonal predictions, historical reconstructions (reanalysis), aquaculture and environmental management including environmental emergency response. Here, we outline the status of existing near-real time ocean observational efforts in polar regions, discuss gaps, and explore perspectives for the future. Specific recommendations include a renewed call for open access to data, especially real-time data, as a critical capability for improved sea ice and weather forecasting and other environmental prediction needs. Dedicated efforts are also needed to make use of additional observations made as part of the Year of Polar Prediction (YOPP; 2017–2019) to inform optimal observing system design. To provide a polar extension to the Argo network, it is recommended that a network of ice-borne sea ice and upper-ocean observing buoys be deployed and supported operationally in ice-covered areas together with autonomous profiling floats and gliders (potentially with ice detection capability) in seasonally ice covered seas. Finally, additional efforts to better measure and parameterize surface exchanges in polar regions are much needed to improve coupled environmental prediction.
  • Article
    Physical 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, Bruno
    This 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.
  • Article
    Sea-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, Julie
    The 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.