On the Impact of Southeastern Pacific-Generated Storm Surges on the Southwestern Atlantic Continental Shelf: Interoceanic Connections Through Coastally Trapped Waves

Abstract

The storm surge in the Southwestern Atlantic Continental Shelf (SWACS) has been characterized as a process forced regionally by migrating atmospheric Rossby waves. When they produce alongshore winds, Ekman transport drives a sea level anomaly that then propagates northward as a Kelvin wave. Here, we explore the hypothesis that Rossby waves on the polar jet stream could generate additional surges in the southeastern Pacific by inverted barometer effect and/or Ekman transport, that then propagate to the SWACS as remotely forced signals connecting both oceans, by means of process-oriented numerical simulations. We find that atmospheric waves initially force a sea level anomaly over the South Pacific Ocean by inverted barometer effect; it increases by the action of alongshore winds when the signal interacts with the coast, and finally enters the SWACS. Remotely generated surge displays strong pseudo-periodicity in a band around 7.5 days and amplitudes of the order of 10% of the regional one. Although remotely and local forced events are independent, they can overlap originating more extreme events. Activity shows a statistically significant seasonal cycle (with mean kinetic energy in winter almost doubling that in summer) and interannual variability (with mean yearly activity almost doubling in some years) at 2–7 years that has increased since 1997, probably due to modulation of the storm tracks by climate variability. Incorporating this process in ocean simulations reduces the forecast/hindcast error of the oceanic surge by 50%.