More test dye releases on a low ebbing tide

We now know that the tide and tidal-inlet velocity are largely in phase – thanks to the WHOI (Raubenheimer & Elgar) AWACS deployment over the weekend.   That information will be posted here later.    Today we did another test dye release.   Recall that previously we did a test dye release at the start of the ebb on medium tide with ENE winds.  The dye flowed down the inlet and then out over the southern ebb shoal – never exiting the “channel”.    We wanted to to see what would happen at a lower tide (the southern ebb shoal is nearly dry) and with more WSW winds.    Check out the photos below.  They were shot from the house balcony in chronological order covering about 15-20 minutes.   We poured in 1 gallon of Rhodamine WT dye @ 23%.

In the first photo below, dye had just released for ~2 min from our boat (in the picture).  It makes a nice small contained patch that is advecting out of the inlet (to the right)

The patch continues to spread out across the deep part of the channel as it is advected out of the inlet

Spreading continues as it is advected below.

This time the dye stays in the limits of the main (“new”) channel not going over the shoals to the south or north.   The principal axis of the dye is angled though.  Dye closer to the southern shoal is advecting offshore more rapidly.  This region is shallow.   Mostly 1.5-2 m deep.

The dye then continues to advect offshore in the center of the main channel.  However, it has now slowed down a LOT.   Note the water depths continue to decrease, between 1-2 m.   There is no strong jet of current at this point.

In the end the dye crossed the channel opening (which had a lot of current induced breaking on it – it is shallow!), but did not really advect much farther offshore.    The strong WSW (sideshore) wind had set up an alongshore current seaward of the shoals.   The dye then slowly advected alongshore to the NE. (+y).     This is fairly different from last time but again no dye went far offshore.   This suggests that putting a wirewalker out at 12 m depth (>1 km offshore of the shoal), is not a good idea.

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