Evidence of Submesoscale Variability in the Solomon Sea: a Glider/Model Study

Glider observations in the Solomon Sea provide a unique set of repeat, high spatial resolution measurements of temperature and salinity spanning the top 1000m of the water column. Because gliders sample slowly, the upper end of the resolved horizontal wavenumber range (wavelength < 50km) is affected by aliased high-frequency oceanic variability; isopycnal quantities however can be analyzed all the way to the glider Nyquist wavenumber (8km). We characterize the spatial distribution of isopycnal temperature variations using the glider data in conjunction with section from model simulations focusing on the submesoscale range (<50 km). Submesoscale isopycnal temperature variation is elevated in layers through the water column: near the surface (affected mainly by conditions in the mixed layer), in the upper thermocline (near the subsurface salinity maximum associated with the South Pacific subtropical water), and on deep isopycnals but predominately in the western boundary current (where the largest subsurface vorticity variance occur). Horizontal wavenumber spectra of observed isopycnal temperature have a slope of -2 through the water column. In physical space, submesoscale isopycnal temperature variations have a vertical to horizontal scale that are near the ratio of the buoyancy frequency to the Coriolis parameter √2(N/f), consistent with quasi-geostrophic theory for stirring of a passive tracer by a mesoscale field and accounting for the one-dimensional glider sampling.