Summer intrusions into Storm Bay, South-East Tasmania (#1013)
The East Australian Current (EAC) mesoscale eddies transport warm nutrient-depleted sub-tropical water down the east coast of Australia to Tasmania. The extension in Tasmania peaks in February and is weakest in winter. When EAC eddies interact with the slope, warm and salty water intrusions can occur into Storm Bay. Cooler nutrient-rich sub-Antarctic water can also reach the shelf edge in summer. While we don't know the exact nature of the interplay between these dynamical processes, it can lead to local changes in ocean temperature and biogeochemistry in Storm Bay, and impact Tasmanian microphytoplankton communities.
Using 8-year of repeat glider mission in Storm Bay, 6-year of mooring data and satellite altimetry data, we investigate the interplay between bottom driven upwelling and EAC eddies in South-east Tasmania. EAC filaments seem to develop along the shelf break when a large quasi-stationary anticyclonic eddy off South East Tasmania impinges on the continental slope. Every summer, this interaction results in a surface intrusion of EAC water, concomitant with a sub-surface intrusion of cold sub-Antarctic water. Using the long timeseries, we assess the characteristics and variability of these simultaneous intrusions. In particular, during the 2016 marine heat wave, two intense intrusions events occur in Storm Bay resulting in large warm and salty anomalies in the surface and large cold and relatively fresher anomalies at depth.