Major Boundary Currents and Inter-basin Flows
How will the key science questions be addressed?
To determine the frequency, form and function (horizontal and vertical) of East Australian Current (EAC) eddies.
Glider deployments will be used to investigate the form and function of EAC eddies, and to fill-in under sampled areas by Argo. Observations by 24 glider deployments over 4 years are required to provide a broad understanding of EAC over different time and space scales (particularly season). The shore-normal mooring arrays will help to clarify the nature of eddy interaction with the continental shelf, upwelling and cross-shelf intrusions and the evolution of the biological response through time series measurements of bio-optical properties. Bio-optical properties in turn, will be validated with direct measurements of phytoplankton pigments and biomass from the NRS. Satellite Remote Sensing is also needed for model initialisation and assessment and glider navigation; to put the glider observations into a regional context, and for sea surface temperature (SST) and surface chlorophyll.
To understand air sea interactions, particularly to determine the development of East Coast Lows and severe winter storms in relation to warm core eddies.
Currently there are no fixed offshore-based meteorological observations in the vicinity of the EAC. It is the intention that the NRS mooring off Port Hacking that will have data telemetered in real time and will also have a surface meteorology package, which will enable the measurement of some of these crucial meteorological parameters, greatly improving the ability to forecast local weather. High frequency based radar observations of meteorological variables above the ocean surface may prove possible in future from the radars that are also planned to be installed.
Quantify the impact of key physical processes such as onshore encroachment of the EAC, slope water intrusions, upwelling, downwelling and internal waves.
HF radar and the mooring array as well as the proposed new hydrographic sampling will allow us to investigate the response as the EAC moves on and off the shelf. Remote sensing provides the spatial context for the data. Biogeochemical sampling and Satellite Remote Sensing will also provide insight into the biology and chemistry of the water column under different EAC scenarios. Ocean gliders provide tracer measurements such as oxygen, salinity and temperature of slope water, while coloured dissolved organic matter (CDOM) fluorescence quantifies proximity to the coast, potential benthic-pelagic coupling and part of the biological response. Each glider is deployed and retrieved on or near the shelf, providing a minimum of 2 cross-shelf transects per deployment, with more possible during weak currents. The cross shelf Slocum transects will provide the most focused data set for observing slope water intrusions and their biological response at depth.