Submesoscale coastal observations and data analysis to understand the surface ocean and geophysical turbulence

Abstract

This talk presents several examples of coastal dynamics and submesoscale turbulence, which are based on (1) remote sensing observations such as altimetry, geostationary ocean color imagery, and high-frequency radars at the O(1)-km spatial resolution and O(1) hour temporal resolution and (2) forward regional circulation model simulations forced with realistic wind stress, tides, and boundary conditions. The dynamics of the surface currents are governed by tides, winds, Coriolis force, low-frequency pressure gradients (less than 0.4 cycles per day), and nonlinear interactions of those forces. Alongshore surface currents show poleward propagating signals with phase speeds of O(10) and O(100 to 300) km day−1 and time scales of 2 to 3 weeks. Submesoscale eddies, identified using flow geometry, have Rossby numbers of 0.1 to 3, diameters in the range of 10 to 60 km, and persistence for 2 to 12 days. The HFR surface currents resolve coastal surface ocean variability continuously across scales from submesoscale to mesoscale (O(1) km to O(1000) km). Their spectra decay with k−2 at high wave number (less than 100 km) in agreement with theoretical submesoscale spectra below the observational limits of present‐day satellite altimeters. Moreover, the studies of dynamics interpretations of the submesoscale sea surface heights and surface currents in the context of the upcoming high-resolution satellite missions are introduced.