Seasonal and inter-annual variation of the Capricorn Eddy, Australia.

The Capricorn Eddy is a cyclone eddy located inside the lee of the Fraser Island and a result of the collisions between the East Australia Current and the Fraser Island, Australia. Since the Capricorn Eddy feeds the upwelling systems and affects greatly the local ecosystem, there is a tremendous value in studying on the Capricorn Eddy. However, the previous studies of the Capricorn Eddy cannot provide a whole picture of its seasonal and inter-annual variations due to the limitation of observation data. In this paper, a new eddy identification method is developed to identify the Capricorn eddy by using the satellite sea level anomaly data over the timeframe from 1995 to 2014. This new approach provides a fast identify method for the Capricorn Eddy and is validated by surface temperature and vorticity calculation. Furthermore, the occurrences and ages of the Capricorn Eddy in the 20-year period are computed. It is demonstrated that Capricorn Eddy is significant seasonal, namely, more frequently Capricorn Eddy appears in Austral summer and less in winter which is supported by the mooring current data. This seasonal variation can attribute to the seasonal East Australian Current variation. By comparing the 20 years inter-annual variation with the Enso event, the trend of the Capricorn Eddy occurrences is similar with the strength of the Enso events but with 1 year time lag. Not only does the long term study of the Capricorn Eddy reveal its relationship with the East Australia Current but also shows that regional circulation can be affected largely by climate change.