Fig 1.
Spatial location, domains and bathymetry of the model grids.
(a) East Australian Current (EAC) model domain with schematic of the main EAC flow overlaid, (b) Hawkesbury Shelf Model (HSM) domain. (c) The location of the observations used for model evaluation including the 3 moorings ORS065, SYD100 and SYD140, and the tide gauge station in Sydney Harbour indicated by the red squares. The 3 shore-normal sections from 0–2000 m used in the analysis are shown at Seal Rocks, Newcastle and Sydney, labelled as S1, S2 and S3 respectively. The horizontal cross-shelf resolution of each model is shown as dx. Colour shading in (a) and (b) represents the depth of the bathymetry (m).
Fig 2.
Domain wide 2-yr mean sea surface temperatures (SST) in oC (top row) and their associated standard deviations (middle row) from (a) AVHRR L3S satellite data, (b) EAC model, (c) HSM. Associated standard deviations are shown in (d-f). (g) Time series of spatially averaged SST (oC) across the domain for time periods with 15% or more satellite (AVHRR) data over the 2 years. Correlation coefficients are shown where cca is the correlation between the satellite and EAC model SST and ccb is the correlation between the satellite and HSM SST.
Fig 3.
EOF analysis of daily geostrophic velocities from the HSM (blue) and satellite (red) for 2012–2013. Spatial structure of the (a) Mean, (b) Mode 1, (c) Mode 2 and (d) Mode 3 showing velocity fields (arrows). Percentages show the variances accounted for by each mode in the model and observations.
Fig 4.
Mean current vectors and variance ellipses of modelled (HSM, black) and observed (red) velocities for 2012–2013 at the location of the 3 moorings off Sydney. Dashed lines show the 100, 1000 and 2000 m isobath; the solid black line shows the location of the 200 m isobath. (a) Upper—depth bin, (b) mid—depth bin, (c) bottom—depth bin and (d) full water column, depth averaged velocities in ms-1.
Fig 5.
Observed (red) and modelled (black) along shore (v, left) and cross-shore (u, right) velocity profiles (ms-1) with depth at the three shelf moorings, ORS065 (a,b), SYD100 (c,d), and SYD140 (e,f). Shading represents the standard deviation and mooring locations are shown in Fig 1.
Fig 6.
Modelled (top panel) and observed (bottom panel) cross-sections of the mean temperature (left column), along-shelf velocity (middle column, negative poleward) and cross-shelf velocity (right column, negative onshore) off Sydney (34oS). The positions of the 3 moorings are indicated by black squares.
Fig 7.
Domain-wide seasonal mean modelled fields.
Velocity fields at the surface (a-d). Velocity vectors show the direction and colour shows the magnitude (ms-1) of the speed. Every 25th vector is shown for clarity. The reference velocity arrow in the bottom right of each panel represents 0.2 ms-1. Domain wide mean SST by season (e-h) and associated standard deviations (i-l) in (oC). Solid black lines show the 100 m and 2000 m isobaths. Area averaged SST (m) showing monthly means for 2012 (black), 2013 (red). Shaded areas represent the standard deviations.
Fig 8.
Box plots showing the along-shelf transport estimates (Sv) through three sections; Seal Rocks (S1), Newcastle (S2) and Sydney (S3), as shown in the map inset.
The transports are shown across three segments a) the inner-shelf (0–100 m isobath) b) mid-shelf (0–200 m isobath), and c) across the outer shelf (200–2000 m isobath) coloured by season. Note the different scales for a, b, and c. As per the legend, the box plots show the median and the mean in red, the box shows the 25th to 75th percentiles, the tails show the 9th and 91st percentile, and the outliers are shown as circles.
Table 1.
Width (km) and area (km 2) of the shelf segments at three sections off Seal Rocks (S1), Newcastle (S2) and Sydney (S3).
Fig 9.
Box plots showing the cross-shelf transport estimates (in Sv) over the shelf, for 3 sections encompassing Seal Rocks (S1x), Newcastle (S2x) and Sydney (S3x) as shown in the map.
Transport a) across the 100 m isobath, b) across the 200 m isobath, and c) across the 2000 m isobath for the 3 sections. Note the different scales for a, b, and c. As per the legend, the box plot shows the median, the mean, the box shows the 25th to 75th percentiles, the tails show the 9th and 91st percentile, and the outliers are shown as circles.
Table 2.
Correlation coefficients of transport between shelf sections.
Fig 10.
Morlet wavelet global power spectrum calculated from the daily transport timeseries, for the along-shelf transport through each of the shelf sections.
(a) 0-100m, (b) 100-200m and (c) 200-2000m and for the across-shelf transport across the (d) 100m (e) 200m and (f) 2000m isobaths. Colours show the transports for each section at Seal Rocks S1, S1x, Newcastle S2, S2x, and Sydney S3, S3x in the along and cross-shelf direction, respectively.
Fig 11.
Identification of the separation latitude of the EAC.
(a) Snapshot of Sea Surface Height (SSH) showing the corresponding SSH isoline used to identify the EAC separation latitude (black line and black dot respectively). Arrows present the surface flow field and solid lines show the isobath (100, 200 and 2000 m). (b) Frequency histogram of the EAC separation latitude calculated within the study domain.
Fig 12.
Schematic diagram representing the three main circulation patterns over the 2-yr period.
(a) Scenario 1, occurring ~ 30% of the time, primarily in summer and autumn, b) Scenario 2 occurring ~20% of the time primarily in summer and autumn and c) Scenario 3 occurring ~ 11% of the time, primarily in winter and spring.
Fig 13.
Snapshots of the three circulation scenarios shown in Fig 12.
SST from the HSM model (left), and SSH with contours every 0.05m (right). Surface current vectors are shown, plotted every 25th grid cell. For (a, b) Scenario 1, 17 Apr 2012, (c, d) Scenario 2, 3 Mar 2013, and (e, f) Scenario 3, 31 May 2013.