Global Internal Tide Model from Satellite Altimetry by Resolving Multiconstituent Multimodal Multidirectional Waves

University Of Washington, Seattle WA

Investigators

Abstract

The global internal tide field is a superposition of waves with multiple tidal frequencies, directions, and modes. To fully understand internal tides, it is necessary to decompose their complex wave field into a series of simpler monochromatic plane waves. The principal investigator has developed a wave decomposition technique suitable for use with data from both satellite sea surface elevation (altimetry) data and numerical simulations that enables the discovery of unprecedented features hidden in the raw internal wave field. This project will further develop the technique and apply it to satellite altimetry covering the global ocean. The results will be used to construct global maps of internal wave tidal components, provide estimates of their seasonal and interannual variability and their contribution to ocean mixing. The accuracy of the satellite observed decomposed internal tides will be evaluated using existing data from field measurements and numerical simulations. The product of this research will be useful for the design of field experiments and modeling of internal tides. In addition, it will benefit research on other ocean processes influenced by internal tides (e.g., primary productivity, ocean acoustics, coral reef bleaching, ocean mixing etc.). A series of animations of internal tide products will be created and shared to the public via YouTube. Some of the animations will also be used to teach children about the ocean and satellite technology. This project will support a full-time graduate student at the University of Washington. Internal tides are ubiquitous in the world oceans but still poorly understood due to the scarcity of field observations with sufficient spatial and temporal resolution. Satellite altimetry is the only practical technique for observing internal tides on the global scale. A previously developed technique applicable to both satellite altimeter data and numerical simulations and capable of decomposing a given internal tide field into multimodal multidirectional waves will be further expanded and applied on a global scale with the aim to: (1) construct global maps of mode-1–3 M2, S2, O1 and K1 internal tides from satellite altimetry; (2) quantify their seasonal and interannual variations; and (3) calculate along-beam decay rates and internal tide driven ocean mixing. The new global internal tide model will consist of separately resolved waves of different frequencies, different baroclinic modes and different horizontal propagation directions. The satellite observed internal tides will be validated against in-situ observations and MITgcm global circulation model simulations. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.