What is the (average) velocity of ocean currents?
This is not meant to be a comprehensive answer:

Sometimes the easiest way to calculate the velocity of an ocean current is to take the published transport of the current and divide by the total depth of the current. 

For instance, for the Agulhas Current, you can take Figure 2 from Casal et al. (2009) (below) and extract the velocities based on the depth of each area. Also in their Figure 6, there are several vertical sections of velocity across the current.    

Also, you can obtain vertical sections of velocity for the same current (Agulhas) in earlier publications: Bryden et al. 2005 (Figure 8 and 9). Or in newer publications: Beal &amp; Elipot (2016).


The main issue is that you will need to do a bit of digging around for each of the currents you list.