Gabriela S. Pilo

During the austral summer of 2017/2018, the Tasman Sea experienced an intense marine heatwave over an extensive area. It persisted for approximately 3 months and caused substantial ecological impacts. The marine heatwave was understood to have been driven primarily by increased net downward heat flux associated with a high pressure system. However, it has been unclear why the marine heatwave persisted. Using an ultra‐high‐resolution (∼1 km) regional ocean model simulation, the drivers, dynamics, and persistence of the 2017/2018 marine heatwave are explored in detail. It is found that a burst of warm water advection helped to initiate the event, but a shallower than usual mixed layer, coupled with near continuous net downward air‐sea heat flux, caused the marine heatwave to persist. Submesoscale dynamics were found to be relatively unimportant to the marine heatwave's persistence.