[(E)]

Another possible action that might have global consequences, digging a tunnel/trench from the ocean to a salt flat that is lower than sea level. This could result in desalination of the ocean (Eventually) and the effects of that are (possibly) global cooling. This could also be used as save the (AtE) world mcguffin.

Lots of reasons to create an inland sea too, 1960s farm the desert mentality leaps to mind. As does the plot to the superman 1(?) movie. I.e. getting coastal real estate.