"On a global scale the oceans are deep and stagnant. Only a skin on the surface is agitated."
How deep is deep?
The surface water in the North Atlantic region sinks to a depth of around 2000 metres due to convection. There it settles on an even denser deep-water layer from the Antarctic that extends down to the sea floor. As the cold and salty surface water sinks by convection, salty water flows in from nearby warmer regions, from the direction of the equator. This water is then cooled in the Arctic air and also begins to sink, so that the convection is continuous. Before sinking, the water absorbs enormous amounts of gases such as carbon dioxide at the sea surface, and then transports them rapidly to much greater depths. That is why the highest concentrations of carbon dioxide in the ocean are found in the convection areas. The high carbon dioxide concentrations pumped into the water by convection have been shown to reach depths today of around 3000 metres. Carbon dioxide is transported relatively rapidly by convection to a depth of 2000 metres. In the North Atlantic the transport to greater depths takes significantly longer because carbon dioxide and other gases can only penetrate the deep water by slow mixing processes.
