ALBERT

Description: Mesoscale eddies are common physical features in the ocean that are important for the transport of heat and momentum, and for the distribution of biochemical materials in the ocean. The existence of an anomalous, poleward flowing surface current, the Leeuwin Current (LC), drives the highest eddy kinetic energy environment among all the global eastern boundary currents off Western Australia (WA). There is a limitation in comprehensive understanding of spatial and temporal variability, in particular, the formation and vertical structure of mesoscale eddies. Therefore, this study aimed to define the climatology and vertical structure of mesoscale eddies off WA. Eddy characteristics were derived off WA (10‒40ºS, 105‒130ºE) using a vector geometry-based eddy detection algorithm applied to daily satellite altimetry data over the period 1993-2020. The vertical structure of cyclonic eddies (CE) and anti-cyclonic eddies (AE) in the Perth canyon were examined using ocean glider data over the period 2010-2017 obtained from the Australian Integrated Marine Observing System (IMOS). The seasonal and inter-annual variability and the lifecycles of mesoscale eddies were documented off WA. Shorter-lived eddy formations (〈30 days) were concentrated along the boundaries of the LC with the CE (AE) along the offshore (inshore) boundary and were related to the generation of vorticity. In contrast to the general phenomenon, the concentrations of Chlorophyll were higher in AE compared to CE whilst both eddy types were hotspots of biological activity in the oligotrophic eastern Indian Ocean.