The circularity of marine microplastics under the influence of climate change

Since plastics were first made in the early 20 century, global plastic production has increased dramatically and annual plastic use reached 460 million metric tons (Mt) in 2019. Although the advent of plastics creates miraculous economic achievements, it brings about severe pollution at the same time. As the life cycle of plastic use worldwide is still in linear form, mismanaged plastic waste might break into microplastics and accumulate in the environment. Rivers are the main route by which plastics enter the ocean. The process may take years or decades for microplastics to reach the ocean. The ocean surface currents were responsible for the transport of plastic waste and the ocean is its ultimate destination. This study correlated the fate of marine microplastics with economic growth under the influence of climate change. Taking 1960 as a benchmark, the trend of world GDP growth coincided with the growth of annual plastic production, indicating that economic growth heavily relies on plastic-related industries. Plastics emit a high amount of greenhouse gas (GHG) through their life span, enhancing the negative impact of climate change, causing the faster weathering process to form microplastics, and further enabling the leakage into the aquatic environment. According to the OECD statistics, 1.7 Mt of plastics entered the ocean system in 2019, reaching the total accumulation of 30 Mt of plastic waste since 1970. Global warming over past decades enhances the Earth's ocean currents which induced the acceleration of ocean plastic distribution. The accelerated ocean transportation may increase plastic accumulation at the garbage patches within five gyres and the Arctic Ocean which are ultimate sinks for plastic waste in the ocean. The abundance of microplastics in the ocean interferes with the carbon fixation capacity of the ocean, forming a nexus implication between climate change, ocean currents, and marine plastic redistribution. The accumulation of marine microplastic is suggested to be a factor in aggravating the impact of climate change. To deal with the dilemma, economic growth should be decoupled with the massive use of plastic utilization to reduce plastic production and GHG emission. Moreover, higher plastic waste recycling is urgently needed to prevent extra microplastics from entering the ocean.