Coastal circulation and eddies generation in the Southwest Mexican Pacific

Abstract. In this work, we investigate if it is possible to identify the Mexican coastal current using satellite data and how this coastal current interacts with the coastline. This study is carried out using the mean sea level anomaly and derived geostrophic velocities from the Copernicus Marine Service from 1993 to 2021. By computing variance ellipses and empirical orthogonal functions for the ocean velocity data, we were able to identify and delineate the coastal current and determine its main characteristics: an average width of 95 km and an average velocity of 0.3 m s^-1. The preferred direction of this coastal current is parallel to the coast, with episodes towards the pole and towards the equators showing seasonal variability. Using a 3D numerical model, we found that the interaction of the coastal current with the coastline generates eddies near the coast in some places forming a wide concavity. The eddies are formed while the current is present (poleward or equatorward), become intense, and move away from the coast until the current weakens. The statistics of some physical variables of near-shore eddies show that they have a similar radius of 30 km and a vorticity of 0.5 X 10^-5 s^-1. We conclude that there is a large number of eddies in the coastal zone of the Mexican Tropical Pacific, and some of these eddies are formed by the interaction of the coastal current with the coast.