Tuesday, 27 June 2017

MOVEMENT OF ARTIFACTS.

Let's, for arguments' sake, say that relatively heavy objects from Waratah were deposited close to shore along the stretch of water between the Bashee and Xora Rivers. Extensive exploration of these waters has not revealed the wreck of the Waratah. How could these objects have come to rest here if there is no wreck of Waratah close by?

If the Waratah did indeed founder in the vicinity of Cape Hermes / Poenskop, what would the pattern of current moving / dragging the objects have been?

We know that the initial current force and direction was part of a cyclonic vortex moving northeastward and then circulating further out to sea reintegrating into the powerful Agulhas mainstream moving southwestward. But this does not explain how objects would then come to lie off the Bashee and Xora Rivers instead of being carried further southwestward ultimately into the southward influence off the Agulhas Bank, much further southwest (Mossel Bay and further).

There is a phenomenon called coastal upwelling which interestingly occurs in the region of the Xora and Bashee Rivers - and further northwest of Cape Hermes. Upstream from these points the general flow is southwestward. The upwelling is one of six large solitary meanders in the Agulhas Current, called Natal Pulses. The upwelling can last for up to three weeks and has been observed over the inner shelf. The cold water at the bottom of the Agulhas stream, dragging objects southwestward, can rise at an average of 1.8 m per day, dragging objects out of the main stream towards the coastline. The plume of the leading edge of the meander can move onshore, reaching speeds of 80 cm / second.

This would be a feasible explanation for anything relating to the Waratah ending up off the Bashee and Xora Rivers without the Waratah necessarily having gone down in the vicinity.

http://www.sciencedirect.com/science/article/pii/S0278434315000850

http://bcre.org.za/seaatlas/papers/port_alfred.pdf



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