Visbeck Martin

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Visbeck
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  • Preprint
    Enhanced warming over the global subtropical western boundary currents
    ( 2011-11) Wu, Lixin ; Cai, Wenju ; Zhang, Liping ; Nakamura, Hisashi ; Timmermann, Axel ; Joyce, Terrence M. ; McPhaden, Michael J. ; Alexander, Michael A. ; Qiu, Bo ; Visbeck, Martin ; Chang, Ping ; Giese, Benjamin
    Subtropical western boundary currents are warm, fast flowing currents that form on the western side of ocean basins. They carry warm tropical water to the mid-latitudes and vent large amounts of heat and moisture to the atmosphere along their paths, affecting atmospheric jet streams and mid-latitude storms, as well as ocean carbon uptake. The possibility that these highly energetic and nonlinear currents might change under greenhouse gas forcing has raised significant concerns, but detecting such changes is challenging owing to limited observations. Here, using reconstructed sea surface temperature datasets and newly developed century-long ocean and atmosphere reanalysis products, we find that the post-1900 surface ocean warming rate over the path of these currents is two to three times faster than the global mean surface ocean warming rate. The accelerated warming is associated with a synchronous poleward shift and/or intensification of global subtropical western boundary currents in conjunction with a systematic change in winds over both hemispheres. This enhanced warming may reduce ocean's ability to absorb anthropogenic carbon dioxide over these regions. However, uncertainties in detection and attribution of these warming trends remain, pointing to a need for a long-term monitoring network of the global western boundary currents and their extensions.
  • Preprint
    Estimating sea-ice coverage, draft, and velocity in Marguerite Bay (Antarctica) using a subsurface moored upward-looking acoustic Doppler current profiler (ADCP)
    ( 2007-09-14) Hyatt, Jason ; Visbeck, Martin ; Beardsley, Robert C. ; Owens, W. Brechner
    A technique for the analysis of data from a subsurface moored upward-looking acoustic Doppler current profiler (ADCP) to determine ice coverage, draft and velocity is presented and applied to data collected in Marguerite Bay on the western Antarctic Peninsula shelf. This method provides sea ice information when no dedicated upward-looking sonar (ULS) data is available. Ice detection is accomplished using windowed variances of ADCP vertical velocity, vertical error velocity, and surface horizontal speed. ADCP signal correlation and backscatter intensity were poor indicators of the presence of ice at this site. Ice draft is estimated using a combination of ADCP backscatter data, atmospheric and oceanic pressure data, and information about the thermal stratification. This estimate requires corrections to the ADCP-derived range for instrument tilt and sound speed profile. Uncertainties of ± 0.20 m during midwinter and ± 0.40 m when the base of the surface mixed layer is above the ADCP for ice draft are estimated based on (a) a Monte Carlo simulation, (b) uncertainty in the sound speed correction, and (c) performance of the zero-draft estimate during times of known open water. Ice velocity is taken as the ADCP horizontal velocity in the depth bin specified by the range estimate.
  • Article
    Atlantic climate variability and predictability : a CLIVAR perspective
    (American Meteorological Society, 2006-10-15) Hurrell, James W. ; Visbeck, Martin ; Busalacchi, Antonio J. ; Clarke, R. A. ; Delworth, T. L. ; Dickson, R. R. ; Johns, William E. ; Koltermann, K. P. ; Kushnir, Yochanan ; Marshall, David P. ; Mauritzen, Cecilie ; McCartney, Michael S. ; Piola, Alberto R. ; Reason, C. ; Reverdin, Gilles ; Schott, F. ; Sutton, R. ; Wainer, I. ; Wright, Daniel G.
    Three interrelated climate phenomena are at the center of the Climate Variability and Predictability (CLIVAR) Atlantic research: tropical Atlantic variability (TAV), the North Atlantic Oscillation (NAO), and the Atlantic meridional overturning circulation (MOC). These phenomena produce a myriad of impacts on society and the environment on seasonal, interannual, and longer time scales through variability manifest as coherent fluctuations in ocean and land temperature, rainfall, and extreme events. Improved understanding of this variability is essential for assessing the likely range of future climate fluctuations and the extent to which they may be predictable, as well as understanding the potential impact of human-induced climate change. CLIVAR is addressing these issues through prioritized and integrated plans for short-term and sustained observations, basin-scale reanalysis, and modeling and theoretical investigations of the coupled Atlantic climate system and its links to remote regions. In this paper, a brief review of the state of understanding of Atlantic climate variability and achievements to date is provided. Considerable discussion is given to future challenges related to building and sustaining observing systems, developing synthesis strategies to support understanding and attribution of observed change, understanding sources of predictability, and developing prediction systems in order to meet the scientific objectives of the CLIVAR Atlantic program.
  • Preprint
    Global Ocean Summit : a forum for institutional coordination of global ocean observations
    ( 2014-11) Cai, Wenju ; Avery, Susan K. ; Leinen, Margaret S. ; Lee, Kenneth ; Lin, Xiaopei ; Visbeck, Martin
    A sustainable global ocean observation system requires timely implementation of a global ocean observation framework. The recent Qingdao Global Ocean Summit offers an effective mechanism for a coherent institutional response to emerging scientific and societal drivers, and for promoting the capacity building in developing economies that is essential for increasing the value and broadening the funding base of the observation system.
  • Article
    Subpolar North Atlantic western boundary density anomalies and the Meridional Overturning Circulation
    (Nature Research, 2021-05-24) Li, Feili ; Lozier, M. Susan ; Bacon, Sheldon ; Bower, Amy S. ; Cunningham, Stuart A. ; de Jong, Marieke F. ; deYoung, Brad ; Fraser, Neil ; Fried, Nora ; Han, Guoqi ; Holliday, Naomi Penny ; Holte, James W. ; Houpert, Loïc ; Inall, Mark E. ; Johns, William E. ; Jones, Sam ; Johnson, Clare ; Karstensen, Johannes ; Le Bras, Isabela A. ; Lherminier, Pascale ; Lin, Xiaopei ; Mercier, Herlé ; Oltmanns, Marilena ; Pacini, Astrid ; Petit, Tillys ; Pickart, Robert S. ; Rayner, Darren ; Straneo, Fiamma ; Thierry, Virginie ; Visbeck, Martin ; Yashayaev, Igor ; Zhou, Chun
    Changes in the Atlantic Meridional Overturning Circulation, which have the potential to drive societally-important climate impacts, have traditionally been linked to the strength of deep water formation in the subpolar North Atlantic. Yet there is neither clear observational evidence nor agreement among models about how changes in deep water formation influence overturning. Here, we use data from a trans-basin mooring array (OSNAP—Overturning in the Subpolar North Atlantic Program) to show that winter convection during 2014–2018 in the interior basin had minimal impact on density changes in the deep western boundary currents in the subpolar basins. Contrary to previous modeling studies, we find no discernable relationship between western boundary changes and subpolar overturning variability over the observational time scales. Our results require a reconsideration of the notion of deep western boundary changes representing overturning characteristics, with implications for constraining the source of overturning variability within and downstream of the subpolar region.