Transmission of ENSO signal to the Indian Ocean

Abstract

The dynamics of El Niño‐Southern Oscillation (ENSO) cycles has previously been interpreted in terms of discharge and recharge of mass and heat in the equatorial Pacific. Some of the ENSO discharge/recharge signals transmit into the Indian Ocean, but the pathway is yet to be fully established. This study reveals a previously un‐noticed subtropical North Pacific (NP) pathway. NP Rossby waves associated with ENSO impinge on the western boundary and move equatorward along the “ray‐path” of Kelvin‐Munk waves, and reflect as equatorial Kelvin waves. En‐route to the equator, the waves are reinforced by wind stress anomalies associated with ENSO. The reflected equatorial Kelvin waves impinge on the Australasian continent and move poleward along the northern western Australia (WA) coast as coastally‐trapped waves, radiating Rossby waves into the south Indian Ocean. In this way, some 55% of the total interannual variance of the WA thermocline is linked to the subtropical NP Rossby waves.

Multi-decadal variations of the South Indian Ocean subsurface temperature influenced by Pacific Decadal Oscillation

“…Several previous studies (e.g. Wijffels and Meyers, 2004;Cai et al, 2005;Schwarzkopf and Böning, 2011) suggested that the westward Pacific Rossby waves excited by zonal winds reach the Pacific west boundaries and reflect Kelvin waves. The reflected Kelvin waves then propagate down the Western Australian coast as coastally trapped waves, radiating Rossby waves into the SIO.…”

Role of El Niño Southern Oscillation (ENSO) Events on Temperature and Salinity Variability in the Agulhas Leakage Region

“…North Pacific Rossby waves generated during ENSO events impinge on the western boundary and move equatorward along the "ray-path" of Kelvin-Munk waves to reflect as equatorial Kelvin waves. When the reflected Kelvin waves impinge upon the Australian continent they become coastally trapped and move poleward along the coast, where they radiate Rossby waves into the south Indian Ocean [16]. Ultimately, an ENSO event triggers two sets of westward-propagating Rossby waves at 12 • S and 25 • S from wind forcing and Kelvin waves, respectively.…”

Evaluating SODA for Indo-Pacific Ocean decadal climate variability studies

“…Furthermore, positive correlation coefficients connect the western tropical North Pacific Ocean with the Indonesian Seas and the tropical South Indian Ocean from lag 0 to 110 (indicated by green arrows and black dashed contour in Figure 3). The transmission of interannual signals from the western tropical Pacific Ocean into the Indian Ocean has been noted in earlier studies and is associated with Rossby waves [Meyers, 1996;Wijffels and Meyers, 2004;Cai et al, 2005;Alory et al, 2007]; however, further analysis of the mechanism is needed considering the long time scale of the IPO. …”