From Richard Jefferys, Berkhamsted, Hertfordshire, UK
The idea you report on to possibly reinforce the vital AMOC ocean current in the Atlantic raises a question: could this only be done using sailing ships or kites? The problem is that a standard ship’s propellers push it along by creating a stream of water in the opposite direction. Adding northwards momentum to AMOC by dragging parachutes through the water would seem to be countered by momentum added in the opposite direction from propellers(5 July, p 11).
