Planetary Wave Signatures Across Three Oceans

Abstract:

Equatorial Deep Jets (EDJs) are vertically stacked east-west currents found around the equator below the thermocline that reverse every few hundred meters. This study evaluates their structure in all three oceans observationally using vertical strain of density profiles from new high-resolution Argo float conductivity-temperature-depth (CTD) instrument profile data from augmented with historical shipboard CTD and lower-resolution Argo float profiles from 1972--2014. Strain profiles are analyzed in a stretched vertical coordinate system determined from the mean vertical density structure. Wavelet decomposition is used to analyze the power spectra in each basin. In the Indian and Pacific Oceans, we see two distinct peaks in the power spectra around the equator, the first a broader Kelvin Wave-like signal and the second a narrower feature consistent with the characteristics of a first-meridional-mode Rossby Wave. In all three ocean basins we find coherent basin-wide signals consistent with first-meridional-mode Rossby Waves, having periods of 5±1 years in the Indian and the Atlantic, and 12±3 years in the Pacific. The first-meridional-mode Rossby wave dispersion relation suggests basin-scale zonal wavelengths in all three oceans. These zonal scales are consistent with those from plane waves fit to the phase, within the large uncertainties of those fits.