Pickering Andrew I.

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Andrew I.

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  • Preprint
    The formation and fate of internal waves in the South China Sea
    ( 2015-03) Alford, Matthew H. ; Peacock, Thomas ; MacKinnon, Jennifer A. ; Nash, Jonathan D. ; Buijsman, Maarten C. ; Centurioni, Luca R. ; Chao, Shenn-Yu ; Chang, Ming-Huei ; Farmer, David M. ; Fringer, Oliver B. ; Fu, Ke-Hsien ; Gallacher, Patrick C. ; Graber, Hans C. ; Helfrich, Karl R. ; Jachec, Steven M. ; Jackson, Christopher R. ; Klymak, Jody M. ; Ko, Dong S. ; Jan, Sen ; Johnston, T. M. Shaun ; Legg, Sonya ; Lee, I-Huan ; Lien, Ren-Chieh ; Mercier, Matthieu J. ; Moum, James N. ; Musgrave, Ruth C. ; Park, Jae-Hun ; Pickering, Andrew I. ; Pinkel, Robert ; Rainville, Luc ; Ramp, Steven R. ; Rudnick, Daniel L. ; Sarkar, Sutanu ; Scotti, Alberto ; Simmons, Harper L. ; St Laurent, Louis C. ; Venayagamoorthy, Subhas K. ; Wang, Yu-Huai ; Wang, Joe ; Yang, Yiing-Jang ; Paluszkiewicz, Theresa ; Tang, Tswen Yung
    Internal gravity waves, the subsurface analogue of the familiar surface gravity waves that break on beaches, are ubiquitous in the ocean. Because of their strong vertical and horizontal currents, and the turbulent mixing caused by their breaking, they impact a panoply of ocean processes, such as the supply of nutrients for photosynthesis1, sediment and pollutant transport2 and acoustic transmission3; they also pose hazards for manmade structures in the ocean4. Generated primarily by the wind and the tides, internal waves can travel thousands of kilometres from their sources before breaking5, posing severe challenges for their observation and their inclusion in numerical climate models, which are sensitive to their effects6-7. Over a decade of studies8-11 have targeted the South China Sea, where the oceans’ most powerful internal waves are generated in the Luzon Strait and steepen dramatically as they propagate west. Confusion has persisted regarding their generation mechanism, variability and energy budget, however, due to the lack of in-situ data from the Luzon Strait, where extreme flow conditions make measurements challenging. Here we employ new observations and numerical models to (i) show that the waves begin as sinusoidal disturbances rather than from sharp hydraulic phenomena, (ii) reveal the existence of >200-m-high breaking internal waves in the generation region that give rise to turbulence levels >10,000 times that in the open ocean, (iii) determine that the Kuroshio western boundary current significantly refracts the internal wave field emanating from the Luzon Strait, and (iv) demonstrate a factor-of-two agreement between modelled and observed energy fluxes that enables the first observationally-supported energy budget of the region. Together, these findings give a cradle-to-grave picture of internal waves on a basin scale, which will support further improvements of their representation in numerical climate predictions.
  • Article
    Climate Process Team on internal wave–driven ocean mixing
    (American Meteorological Society, 2017-12-01) MacKinnon, Jennifer A. ; Zhao, Zhongxiang ; Whalen, Caitlin B. ; Waterhouse, Amy F. ; Trossman, David S. ; Sun, Oliver M. ; St. Laurent, Louis C. ; Simmons, Harper L. ; Polzin, Kurt L. ; Pinkel, Robert ; Pickering, Andrew I. ; Norton, Nancy J. ; Nash, Jonathan D. ; Musgrave, Ruth C. ; Merchant, Lynne M. ; Melet, Angelique ; Mater, Benjamin D. ; Legg, Sonya ; Large, William G. ; Kunze, Eric ; Klymak, Jody M. ; Jochum, Markus ; Jayne, Steven R. ; Hallberg, Robert ; Griffies, Stephen M. ; Diggs, Stephen ; Danabasoglu, Gokhan ; Chassignet, Eric P. ; Buijsman, Maarten C. ; Bryan, Frank O. ; Briegleb, Bruce P. ; Barna, Andrew ; Arbic, Brian K. ; Ansong, Joseph ; Alford, Matthew H.
    Diapycnal mixing plays a primary role in the thermodynamic balance of the ocean and, consequently, in oceanic heat and carbon uptake and storage. Though observed mixing rates are on average consistent with values required by inverse models, recent attention has focused on the dramatic spatial variability, spanning several orders of magnitude, of mixing rates in both the upper and deep ocean. Away from ocean boundaries, the spatiotemporal patterns of mixing are largely driven by the geography of generation, propagation, and dissipation of internal waves, which supply much of the power for turbulent mixing. Over the last 5 years and under the auspices of U.S. Climate Variability and Predictability Program (CLIVAR), a National Science Foundation (NSF)- and National Oceanic and Atmospheric Administration (NOAA)-supported Climate Process Team has been engaged in developing, implementing, and testing dynamics-based parameterizations for internal wave–driven turbulent mixing in global ocean models. The work has primarily focused on turbulence 1) near sites of internal tide generation, 2) in the upper ocean related to wind-generated near inertial motions, 3) due to internal lee waves generated by low-frequency mesoscale flows over topography, and 4) at ocean margins. Here, we review recent progress, describe the tools developed, and discuss future directions.