Topographically Trapped Waves Around South America With Periods Between 40 and 130 Days in a Global Ocean Reanalysis.

The South American continental slope hosts a variety of topographic waves. We use a 27‐year‐long global ocean reanalysis (1/12° Spatial resolution) to examine trapped waves (TWs) around South America at periods ranging from 40 to 130 days. The waves propagate from the Equatorial Pacific to the Tropical Atlantic (22°S) with phase velocities between 1.8 and 7 m/s according to the local background characteristics, such as stratification, slope steepness, latitude, mean flow and shelf width. The Madden‐Julian Oscillation (MJO) plays a key role in forcing the TWs in two ways (a) through an oceanic connection implying equatorial Kelvin waves reaching the western American Coast and (b) through an atmospheric teleconnection enhancing southerly winds in the south‐east Pacific. Furthermore, local winds, not necessarily linked with the MJO, modulate and trigger waves in specific locations, such as the Brazil‐Malvinas Confluence. Trapped waves impact the along‐shore currents: during the positive phase of the waves the near‐surface flow is enhanced by about 0.1 m/s. Plain Language Summary: Several waves propagate around South America from the Equatorial Pacific to the Tropical Atlantic (22°S) along the continental slope. The waves propagate relatively fast with velocities varying between 1.8 and 7 m/s depending on the local background for example, the continental slope geometry. Two forcing mechanisms were identified: a Pacific Equatorial forcing associated with climatic indices and a local wind forcing at specific locations such as the south‐east Pacific and the Brazil‐Malvinas Confluence. The waves impact the along‐shore currents: the flow is modulated by about 0.1 m/s. Key Points: Coherent Sea Level Anomalies indicate trapped waves propagation along the slope from the Equatorial Pacific to the Tropical Atlantic (22°S)The Madden‐Julian Oscillation (MJO), through oceanic and atmospheric teleconnections, plays a key role in forcing the trapped wavesFurthermore, local winds trigger waves in specific locations, such as the south‐east Pacific and the Brazil‐Malvinas Confluence [ABSTRACT FROM AUTHOR]