What is the reason 'THE GRAND BANKS OF NEWFOUNDLAND'extending southward and becoming more shallow?

Question

South of Newfoundland(Canada) there is a shallow bank called 'Grand banks of Newfoundland' and its southern part is extending more south wards and the depth of water over the banks also decreasing.

Answer 1

Likely the depth of the banks is related to the sediment delivered there (even long ago).  That may depend in part on the location of rivers and even seasonal changes in flow.