Blue-shifted deep ocean currents in the equatorial Indian Ocean

Spectra from two decades of zonal current data at $$\sim $$ 4000 m in the central and western equatorial Indian Ocean show a shift dominant frequencies west to east. The 120–180-day period is stronger 77 $$^\circ E, 60–120-day 83 30–90-day 93 E. weakening lower near eastern boundary can be explained using theoretical ray paths Kelvin waves reflected Rossby waves. wave forced by winds reflects as with different meridional modes. After reflection, low (high) frequency beams travel larger (shorter) distance before reaching bottom, thereby creating shadow zone, region energy, between path boundary. longitude not evident top 1000 m, where dominated semi-annual cycle.