Investigating the role of submesoscale eddies for the accumulation of floating plastic debris in the eastern North Pacific Ocean

Abstract

Buoyant plastic debris is an increasing source of pollution threatening marine environments. As floating plastic debris moves from the shore to the open ocean, they are found to accumulate in large-scale converging circulation patterns called subtropical gyres or garbage patches. Previous in-situ observations give insight into the spatial heterogeneity distribution of floating marine debris at the ocean surface. However, minimal research has yet to take into account how submesoscale eddies, ocean circulation patterns described as 1-100 km diameter vorticities, can influence the accumulation and transport of floating plastic debris at the sea surface. Traditionally, there are two types of submesoscale eddies, cyclonic (a counterclockwise low pressure rotational dispersal system) and anti-cyclonic (a clockwise high pressure rotational accumulation system). The aim of this study is to investigate how the abundance, weight, characteristics, and variability of buoyant plastic debris is influenced by cyclonic and anti-cyclonic submesoscale eddies analyzed from three different regions in relation to the Great Pacific Garbage Patch (GPGP). Using daily satellite observations to identify anti-cyclonic and cyclonic submesoscale formations, floating plastic debris was extracted from the sea surface outside the GPGP, in the transition zone into the GPGP, and inside the GPGP. Due to the anti-cyclonic accumulating rotational dynamic, it is hypothesized that anti-cyclonic submesoscale eddies will accumulate a higher concentration of floating plastic debris in comparison to cyclonic submesoscale eddies. The results demonstrate a trend of cyclonic eddies accumulating higher concentrations than anti-cyclonic eddies within the outside and the transition zone into the GPGP. While anti-cyclonic eddies show a trend in accumulating higher concentrations of floating plastic debris inside the GPGP. Hard (‘H’) type plastics with the size range between 0.05 cm to 0.15 cm (Micro 1) was a common trend also found within the anti-cyclonic submesoscale measurements. While this study highlights how physical oceanic processes impact the dispersal of floating plastic debris, further research is required into plastic debris distribution patterns since these findings exhibited large spatial heterogeneity distribution of floating plastic debris found within submesoscale eddies.