Generation of Low‐Latitude Seamount‐Trapped Waves: A Case Study of the Seychelles Plateau. Issue 8 (9th August 2021)

• Record Type: Journal Article
• Authors: Arzeno‐Soltero, Isabella B.; Giddings, Sarah N.; Pawlak, Geno; McClean, Julie L.; Wang, He; Rainville, Luc; Lee, Craig M.
• Is Part Of: Journal of geophysical research. Volume 126:Issue 8(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-08-09
• Subjects: Yanai -- trapped wave -- seamount -- Seychelles -- Indian Ocean -- equatorial; Oceanography -- Periodicals; 551.4605
• DOI: 10.1029/2021JC017234
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: Baroclinic seamount‐trapped waves are thought to influence their surrounding ecosystem; however, trapped waves are not well‐studied in near‐equatorial settings, where stratification is strong and Burger numbers ( S = N 2 H 2 f 2 L H 2 ) are large. Motivated by observations, we use daily output (2005–2009) from the global Parallel Ocean Program Model (POP) to examine topographically trapped baroclinic waves around the Seychelles Plateau ( S > 400 ) in the tropical Indian Ocean. These trapped waves are associated with velocity and temperature oscillations at periods of 15–16 days, similar to the dominant period of some equatorial Yanai waves. Energy flux maps using POP output suggest that quasi‐biweekly equatorial Yanai waves excite trapped waves on the western and south‐western flanks of the Seychelles Plateau, near the surface. The anticyclonic energy flux associated with the trapped wave extends vertically throughout the water column and around most of the plateau circumference, diminishing on the eastern flank of the plateau. This work highlights the role that equatorial planetary waves and trapped waves play in facilitating energy redistribution, dissipation, and mixing in the tropical ocean. Plain Language Summary: Oceanic internal waves (waves in the interior of the ocean) that propagate around seamounts are thought to contribute to ecological productivity, yet there is a lack of research on the dynamics of these processes in the tropics. We refer to these particular internal oscillations as "trapped waves" because they propagate along a topographic slope, rather than radiating away in the ocean as free waves. Motivated by observations, we use five years (2005–2009) of daily output from a global numerical model (POP) to study trapped waves around the Seychelles Plateau in the tropical Indian Ocean. These oscillations cause changes in the velocity and temperature at periods of 15–16 days, resembling the dominant periods of some waves along the equator (Yanai waves). We created maps of energy pathways using POP output; these suggest that Yanai waves excite the plateau‐trapped waves near the surface, along the western and south‐western flanks of the plateau. The trapped waves propagate energy vertically throughout the water column and around the plateau until they reach the eastern side of the plateau, where the energy decays. This work highlights the role of equatorial waves and trapped waves in redistributing energy, and facilitating turbulence and mixing in the tropical ocean. Key Points: Model output suggests Yanai waves generate trapped waves around the Seychelles Plateau Yanai wave energy flux is surface‐intensified along the western and south‐western plateau edges Trapped waves flux energy throughout the water column and around the plateau circumference