There’s a clockwise-rotating eddy dominating the flow off Whangaroa and the Bay of Islands at the moment. This is called a cyclonic or cool core eddy in the southern hemisphere. Note that the flow direction is the opposite for cool core eddies in the northern hemisphere. You can see the eddy outlined by the current flow arrows, where I’ve placed a red circle in Figure 1.
The cyclonic eddy raises cooler, deeper water towards the surface. This can be seen as a cool patch of surface water in the SST maps over the last 4 days. The cool water is marked by the blue circle in Figure 2.
Cyclonic (clockwise) eddies in the southern hemisphere have lower sea surface height (SSH) and a doming thermocline. This means that the cooler, deeper water inside the eddy is displaced upward, which brings nutrients into the lighted waters near to the surface. The nutrient enrichment allows phytoplankton to grow quickly, so these eddies tend to show areas with higher chlorophyll. In this case, you can see concentrations of chlorophyll around the edge of the eddy (marked by the red arrows on the chlorophyll maps in Figure 3). On the most recent day, the chlorophyll patches have been sheared apart into streaks running parallel to shore by the alongshore current.
By the latest day, the alongshore current (highlighted by the red arrow on the currents map in figure 4) has created two clear frontal zones (marked by red arrows on the SST and fronts maps in Figure 5 and 6). These are likely areas for plankton feed to accumulate, which will also be an attractive feeding area for large pelagic fishes.
Get your monthly, 6 month or one year subscription here https://www.fishingmaps.info/store/ or use the one-off monthy option as a trial.
#FishingMaps #SportFishing #tuna #marlin