I wonder how that will affect the Amazon rainforest since it receives phosphorus and other nutrients blown of the Atlantic from the Sahara desert. If salt starts getting blown over too I wonder if that will ruin the soil fertility there.

Was going to say this, there are/have been many ideas to do just this - one was to build a huge canal and just then let the sea flood the area...

Also - there are lots of un-earthed treasures to be found under the saharan which was once a lush environ and have been covered with sand - so prior to flooding it, we need to lidar and excavate it.

What if we vaccuumed up all the sand and built a new island/continent with the material and just revealed everything underneath - then flooded it. (I believe UAE is in the market for more sand-built-land-masses)

One of the more feasible ones was a linear greenhouse with a canal in it.

I'm sure someone has done the math to figure out what the proper length is for such a canal, to avoid problems with scaling. And if you've ever been near an ocean for much time, you know the salt tends to get around. So I'm not sure how in a multi-year project you keep that to a minimum.