Evaluating uncertainties and multi-wave interference patterns in internal tides observed by satellite altimetry

James Girton (University of Washington, United States)


Zhongxiang Zhao (University of Washington, USA); Matthew Alford (University of Washington, USA)

Event: 2014 Ocean Surface Topography Science Team Meeting

Session: Tides, internal tides and high-frequency processes

Presentation type: Type Poster

Internal tides (internal waves generated by tidal flow over steep
topography seen radiating across ocean basins) have been observed in
great detail by fitting low-mode plane waves to multi-altimeter datasets in
small sliding sub-regions. This technique is able to identify multiple
waves in a given location, but connecting the waves to generation
sites requires a certain amount of subjective interpretation.
In addition, the surface height signal of the internal tide is
typically one to two orders of magnitude smaller than that due to
mesoscale eddies, presenting a need to evaluate the the statistical
significance of the wave-fitting results in a low signal-to-noise
ratio environment.

We explore several methods for objectively grouping internal tide
waves into coherent beams and connecting these to topographic
generation sites. In order to do this, we have also developed complementary
methods for evaluating the uncertainty in satellite-derived internal
tide amplitude and direction and shown that low-mode internal tides are
separable from noise over most of the ocean. The regions of
significance diminish in size for the lower-amplitude tidal
constituents and for higher vertical mode numbers.
James Girton
University of Washington
United States