Does the Walker circulation create the Trade winds or vice versa?

At the end of the 1960s the Norwegian-American meteorologist Jacob(Jack) Bjerknes was the first to  link variations in the tropical Pacific Ocean with large-scale motions in the tropical atmosphere and the appearance of El Niño.

Note that we are talking about the atmosphere above the prevailing weather (if one may say so). These movements are one of the strongest driving forces behind the Trade Winds.

During a normal year with warm water over the Indonesian archipelago and the colder waters outside South America, a gigantic sea breeze-like circulation(Walker cisrculation) with ascending air (low pressure), prevails over the western Pacific equatorial parts, and the opposite, falling air in the east (high pressure).

When the hot water during an El Niño episode spreads eastward, also the Walker Circulation moves eastward. This in turn affects the circulation over Africa and South America and thus most of the tropics.

What the scientists appear not to agree upon is whether it is the water masses fleeing eastward which makes the Walker circulation to move, or vice versa. This may well be a running point when reasoning about climate change and El Niño.