These tend to dominate the passive transport of any floating objects. The ocean circulation is driven by the complex interaction of atmospheric forcing (winds), the Coriolis force due to the Earth’s rotation, density differences (temperature and salinity) and deep-water formation in the Arctic and sub-Arctic seas and Southern Ocean (Thermo-Haline circulation due to the sinking of cold, dense water, produced through the formation of freshwater ice) (Lozier 2015). Within these broad patterns the circulation is highly complex and variable, on multiple scales in space (mm - 100s km) and time (s - decades) (Figure 6.2). This will have a significant influence on the distribution of floating plastics, providing an explanation for some of the spatial and temporal variability in concentrations that have been observed. The water column is not uniform in temperature and salinity. The upper few metres of the ocean will be mixed by wave action episodically.