Impact of windage on ocean surface Lagrangian coherent structures

Windage, the additional direct, wind-induced drift of material floating at the free surface of the ocean, plays a crucial role in the surface transport of biological and contaminant material. Lagrangian coherent structures (LCS) uncover the hidden organizing structures that underlie material transport by fluid flows. Despite numerous studies in which LCS ideas have been applied to ocean surface transport scenarios, such as oil spills, debris fields and biological material, there has been no consideration of the influence of windage on LCS. Here we investigate and demonstrate the impact of windage on ocean surface LCS via a case study of the ocean surrounding the UNESCO World Heritage Ningaloo coral reef coast in Western Australia. We demonstrate that the inclusion of windage is necessary when applying LCS to the study of surface transport of any floating material in the ocean.