Eastern Pacific High Sea

The tropical eastern Pacific stretches between the open ocean and the western shores of the Americas, including the maritime approaches to Central America and Colombia. At about five degrees north, the Pacific reaches its greatest east-west width, roughly 10,700 nautical miles from Indonesia to the Colombian coast. Near the Equator, heavy rainfall makes surface water less salty than at many higher latitudes; salinity there can fall to about 34 parts per thousand.

Warm water and humid air support powerful seasonal weather. The eastern Pacific is one of the world's two most active tropical-cyclone basins. Hurricanes form south of Mexico between June and October, sometimes striking the Mexican coast and occasionally reaching the southwestern United States. The El Nino Southern Oscillation adds another account of variation: when three-month sea-surface temperatures depart by more than half a degree Celsius above or below normal, conditions are classified as El Nino or La Nina. These shifts affect rainfall, winds and the broader circulation of the tropical ocean.

Spanish navigators brought the region into written transoceanic history. Balboa crossed the Isthmus of Panama in 1513 and named the Pacific Mar del Sur, and ships later sailed from Mexico and Peru to the Philippines via Guam. The tropical eastern Pacific therefore combines humid equatorial water, destructive storms and an early route linking the American coasts with Asia.