Observational Constraints on the Submesoscale Sea Surface Height Variance of Balanced Motion

– Charly de Marez, Scientist, California Institute of Technology –

Résumé :

Oceanic currents with horizontal scales smaller than 100 km are a major part of the oceanic circulation.
We do not currently have a global characterization of these submesoscale flows and their impact.
Even if presently available satellite altimetry data are pushed to their limit, their resolution is about 100 km, such that the submesoscales is still not accessible.
The Surface Water and Ocean Topography (SWOT) mission, scheduled for launch in late 2022, is expected to lower the noise floor by a factor of 50 compared to nadir altimeters, giving access to finer scales.The sea surface height (SSH) field at these finer scales, however, is expected to be a jigsaw puzzle of signatures due to geostrophic (balanced) turbulence and internal gravity waves.
One will have to distinguish between signals arising from these drastically different types of motion in order to correctly interpret the new data.

Clear expectations for the variance of these signals will help with this distinction.
We here present such expectations for the power spectrum of SSH, widely used as a low-order statistical descriptor of this variance and its space–time scales.
We focus on the balanced part of the signal as it is primarily this part of the flow that transport tracers.

We present two methods to constrain a spectral model of the wavenumber-frequency content of balanced SSH variance, using a pair of GPS buoys and a combination of moored current meters and altimetry.
We show that the observations are consistent with SSH variance spectra that drop off steeply in wavenumber, even in the presence of active submesoscale currents.
We discuss implications of these results for the upcoming SWOT mission and offer some comments on the global frequency content of balanced flow.

Lien Zoom :

https://univ-tlse3-fr.zoom.us/j/96652520492?pwd=VXF6ZFJHdWxxRnVwNlgvVXhMQU0rQT09

ID de réunion : 966 5252 0492
Code secret : 724539