Why do floating plastic wastes collect in subtropical ocean gyres?

Floating plastic waste accumulates in subtropical ocean gyres primarily due to the large-scale, wind-driven circulation patterns of these regions. Subtropical gyres are anticyclonic circulation features that act as massive, rotating systems—clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere—that effectively draw in and trap solid matter, such as plastics, from surrounding currents.1234

These gyres cover approximately 40 percent of the world's oceans. As debris is transported by various ocean currents from coastal areas toward the center of these gyres, it becomes concentrated in zones often referred to as "garbage patches". Because synthetic plastics are largely nonbiodegradable, they persist in these environments for years, eventually breaking down into smaller microplastics through photodegradation caused by sunlight and seawater. This process creates a persistent "soup" of plastic particles that remains trapped within the rotational flow of the gyres.215