Microplastics in the cryosphere - a potential time bomb?

Microplastics (MPs) have been detected in many parts of the world in snow, hail, sea ice, glaciers, and permafrost. The ubiquity of microplastic around the globe means that there is a need to focus on its circulation dynamics in the Earth's diverse ecosystems; the prominence of MP fibers, which has been indicated as of human clothing and activities, in high altitude frozen water is explained by their enhanced suspension in the air, allowing them to be transported over long distances from urban centers. The MP particles can act as nucleation centers for ice crystals and, once incorporated, reduce the albedo (reflective capacity) of the frozen mass, causing temperature increases. However, cores have indicated that ice in glaciers may remain frozen for thousands of years. This article reviews the quantities and types of MPs that have been detected in snow, hail, sea ice, and glaciers. The potential for release of these, as well as MPs in the permafrost, following global warming, is discussed. As the global warming process evolves, these sites will act as additional sources of MPs accumulated over the course of recent human history. It is important to be aware of the future entry of microplastic into the global environment from these sources, especially into the already fragile extreme ecosystems of the cryosphere.