We hear it over and again: the melting ice in Greenland due to warming will soon lead to a collapse of the AMOC, making it difficult for it to “restart”.
The salt content in the north is critical because the salt-rich tropical water cools down and sinks due to the higher salt content, which is the “pump” that makes circulation possible in the first place. It also transports very large amounts of heat into the North Atlantic.
Scenarios have been published that calculate a drastic cooling of the greater area (especially Europe) around it if the AMOC is “switched off”. The “Day after Tomorrow” scenario.
A more recent summary of these “tipping point” assumptions comes from Prof. Rahmstorf. It refers to reconstructed phases of such collapses, especially during “Heinrich Events” in the last ice age. At that time, large quantities of icebergs advanced far to the south, where they melted and thus probably brought the AMOC to a standstill through sweetening.
New paper finds no alarm
A completely new paper sheds light on these events in detail and reconstructs the freshwater inputs very precisely. A very detailed discussion can be found here.
Hellbound and Down 