How might thermohaline circulation be turned off?
Thermohaline circulation is driven by the sinking of cold, salty water at high latitudes. Fresh water flowing into the North Atlantic Ocean from rainfall or the melting of ice and permafrost can make the ocean water less salty, and therefore less dense. If it becomes “light” enough, it will not sink any more, possibly slowing or shutting down global thermohaline circulation. Indeed, during some of the abrupt events in Earth’s past climate, scientists find evidence of large catastrophic flows of fresh water into the North Atlantic from the melting of glaciers and ice caps, and due to flooding from glacier-dammed lakes. Without the large-scale sinking of salty water in the North Atlantic the influx of warm water to replace it from the tropics would not occur, effectively switching off the thermohaline circulation. Past changes in thermohaline circulation have occurred during periods of relatively rapid climate change, such as transitions in and out of glaciations. Similarly, the rapid wa
