title: The formation and fate of internal waves in the South China Sea.
abstract: 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 affect a panoply of ocean processes, such as the supply of nutrients for photosynthesis, sediment and pollutant transport and acoustic transmission; they also pose hazards for man-made structures in the ocean. Generated primarily by the wind and the tides, internal waves can travel thousands of kilometres from their sources before breaking, making it challenging to observe them and to include them in numerical climate models, which are sensitive to their effects. For over a decade, studies have targeted the South China Sea, where the oceans' most powerful known internal waves are generated in the Luzon Strait and steepen dramatically as they propagate west. Confusion has persisted regarding their mechanism of generation, variability and energy budget, however, owing to the lack of in situ data from the Luzon Strait, where extreme flow conditions make measurements difficult. Here we use new observations and numerical models to (1) show that the waves begin as sinusoidal disturbances rather than arising from sharp hydraulic phenomena, (2) reveal the existence of >200-metre-high breaking internal waves in the region of generation that give rise to turbulence levels >10,000 times that in the open ocean, (3) determine that the Kuroshio western boundary current noticeably refracts the internal wave field emanating from the Luzon Strait, and (4) demonstrate a factor-of-two agreement between modelled and observed energy fluxes, which allows us to produce an 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.
authors.affiliation: 1] Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92037, USA [2] University of Washington, Seattle, Washington 98105, USA.
authors.forename: Matthew H
authors.initials: MH
authors.lastname: Alford
authors.affiliation: Massachusetts Institute of Technology (MIT), Cambridge, Massachusetts 02139, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Peacock
authors.affiliation: Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92037, USA.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: MacKinnon
authors.affiliation: Oregon State University, Corvallis, Oregon 97370, USA.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Nash
authors.affiliation: University of Southern Mississippi, Stennis Space Center, Mississippi 39529, USA.
authors.forename: Maarten C
authors.initials: MC
authors.lastname: Buijsman
authors.affiliation: Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92037, USA.
authors.forename: Luca R
authors.initials: LR
authors.lastname: Centurioni
authors.affiliation: Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92037, USA.
authors.forename: Luca R
authors.initials: LR
authors.lastname: Centuroni
authors.affiliation: University of Maryland, Cambridge, Maryland 21613, USA.
authors.forename: Shenn-Yu
authors.initials: SY
authors.lastname: Chao
authors.affiliation: Institute of Oceanography, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Ming-Huei
authors.initials: MH
authors.lastname: Chang
authors.affiliation: University of Rhode Island, Rhode Island 02882, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Farmer
authors.affiliation: Stanford University, Stanford, California 94305, USA.
authors.forename: Oliver B
authors.initials: OB
authors.lastname: Fringer
authors.affiliation: National Sun-Yat Sen University, Kaohsiung 80424, Taiwan.
authors.forename: Ke-Hsien
authors.initials: KH
authors.lastname: Fu
authors.affiliation: Naval Research Laboratories (NRL), Stennis Space Center, Mississippi 39529, USA.
authors.forename: Patrick C
authors.initials: PC
authors.lastname: Gallacher
authors.affiliation: University of Miami, Miami, Florida 33149, USA.
authors.forename: Hans C
authors.initials: HC
authors.lastname: Graber
authors.affiliation: Woods Hole Oceanographic Institution, Falmouth, Massachusetts 02543, USA.
authors.forename: Karl R
authors.initials: KR
authors.lastname: Helfrich
authors.affiliation: Florida Institute of Technology, Melbourne, Florida 32901, USA.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Jachec
authors.affiliation: Global Ocean Associates, Alexandria, Virginia 22310, USA.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Jackson
authors.affiliation: University of Victoria, Victoria, British Columbia V8W 3P6, Canada.
authors.forename: Jody M
authors.initials: JM
authors.lastname: Klymak
authors.affiliation: Naval Research Laboratories (NRL), Stennis Space Center, Mississippi 39529, USA.
authors.forename: Dong S
authors.initials: DS
authors.lastname: Ko
authors.affiliation: Institute of Oceanography, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Sen
authors.initials: S
authors.lastname: Jan
authors.affiliation: Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92037, USA.
authors.forename: T M Shaun
authors.initials: TM
authors.lastname: Johnston
authors.affiliation: Princeton University, New Jersey 08542, USA.
authors.forename: Sonya
authors.initials: S
authors.lastname: Legg
authors.affiliation: National Sun-Yat Sen University, Kaohsiung 80424, Taiwan.
authors.forename: I-Huan
authors.initials: IH
authors.lastname: Lee
authors.affiliation: University of Washington, Seattle, Washington 98105, USA.
authors.forename: Ren-Chieh
authors.initials: RC
authors.lastname: Lien
authors.affiliation: Institut de Mécanique des Fluides de Toulouse, Toulouse 31400, France.
authors.forename: Matthieu J
authors.initials: MJ
authors.lastname: Mercier
authors.affiliation: Oregon State University, Corvallis, Oregon 97370, USA.
authors.forename: James N
authors.initials: JN
authors.lastname: Moum
authors.affiliation: Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92037, USA.
authors.forename: Ruth
authors.initials: R
authors.lastname: Musgrave
authors.affiliation: Korea Institute of Ocean Science and Technology, Ansan 426-744, South Korea.
authors.forename: Jae-Hun
authors.initials: JH
authors.lastname: Park
authors.affiliation: 1] University of Washington, Seattle, Washington 98105, USA [2] Massachusetts Institute of Technology (MIT), Cambridge, Massachusetts 02139, USA.
authors.forename: Andrew I
authors.initials: AI
authors.lastname: Pickering
authors.affiliation: Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92037, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Pinkel
authors.affiliation: University of Washington, Seattle, Washington 98105, USA.
authors.forename: Luc
authors.initials: L
authors.lastname: Rainville
authors.affiliation: Soliton Ocean Services, Carmel, California 93924, USA.
authors.forename: Steven R
authors.initials: SR
authors.lastname: Ramp
authors.affiliation: Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92037, USA.
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Rudnick
authors.affiliation: University of California San Diego, La Jolla, California 92037, USA.
authors.forename: Sutanu
authors.initials: S
authors.lastname: Sarkar
authors.affiliation: University of North Carolina, Chapel Hill, North Carolina 25599, USA.
authors.forename: Alberto
authors.initials: A
authors.lastname: Scotti
authors.affiliation: University of Alaska at Fairbanks, Fairbanks, Alaska 99775, USA.
authors.forename: Harper L
authors.initials: HL
authors.lastname: Simmons
authors.affiliation: Woods Hole Oceanographic Institution, Falmouth, Massachusetts 02543, USA.
authors.forename: Louis C
authors.initials: LC
authors.lastname: St Laurent
authors.affiliation: Colorado State University, Fort Collins, Colorado 80523, USA.
authors.forename: Subhas K
authors.initials: SK
authors.lastname: Venayagamoorthy
authors.affiliation: National Sun-Yat Sen University, Kaohsiung 80424, Taiwan.
authors.forename: Yu-Huai
authors.initials: YH
authors.lastname: Wang
authors.affiliation: Institute of Oceanography, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Joe
authors.initials: J
authors.lastname: Wang
authors.affiliation: Institute of Oceanography, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Yiing J
authors.initials: YJ
authors.lastname: Yang
authors.affiliation: Office of Naval Research, Arlington, Virginia, USA.
authors.forename: Theresa
authors.initials: T
authors.lastname: Paluszkiewicz
authors.affiliation: Institute of Oceanography, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Tswen-Yung David
authors.initials: TY
authors.lastname: Tang